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CBSE Questions for Class 12 Commerce Maths Relations And Functions Quiz 4 - MCQExams.com
CBSE
Class 12 Commerce Maths
Relations And Functions
Quiz 4
If
f
:
(
3
,
6
)
→
(
1
,
3
)
is a function defined by
f
(
x
)
=
x
−
[
x
3
]
(
where
[
.
]
denotes the greatest integer function
)
,
then
f
−
1
(
x
)
=
Report Question
0%
x
−
1
0%
x
+
1
0%
x
0%
none of these
Explanation
Given that
f
(
x
)
=
x
−
[
x
3
]
where
f
:
(
3
,
6
)
→
(
1
,
3
)
Now, inside the given domain, we will always have
[
x
3
]
=
1
∴
f
(
x
)
=
x
−
1
throughout its domain
⇒
y
=
x
−
1
⇒
x
=
y
+
1
=
f
−
1
(
y
)
∴
f
−
1
(
x
)
=
x
+
1
Let
g
(
x
)
=
1
+
x
−
[
x
]
and
f
(
x
)
=
{
−
1
x
<
0
0
x
=
0
1
x
>
0
Then for all
x
,
f
{
g
(
x
)
}
is equal to
Report Question
0%
x
0%
1
0%
f
(
x
)
0%
g
(
x
)
Explanation
Let
g
(
x
)
=
1
+
x
−
[
x
]
=
1
+
{
x
}
>
0
since
{
x
}
∈
[
0
,
1
)
∀
x
∈
R
Hence
f
{
g
(
x
)
}
=
1
The inverse of the function
f
(
x
)
=
log
2
(
x
+
√
x
2
+
1
)
is
Report Question
0%
2
x
+
2
−
x
0%
2
x
+
2
−
x
2
0%
2
−
x
−
2
x
2
0%
2
x
−
2
−
x
2
Explanation
We have to find the inverse of
f
(
x
)
which means
f
is one one and onto function
Let
f
(
x
)
=
y
=
log
2
(
x
+
√
x
2
+
1
)
∴
2
y
=
x
+
√
x
2
+
1
...(i)
2
−
y
=
1
x
+
√
x
2
+
1
=
√
x
2
+
1
−
x
1
...(ii)
By subtracting (i) and (ii) we have
∴
2
y
−
2
−
y
=
2
x
or
x
=
1
2
(
2
y
−
2
−
y
)
∴
f
−
1
(
y
)
=
1
2
(
2
y
−
2
−
y
)
Replace
y
→
x
∴
f
−
1
(
x
)
=
1
2
(
2
x
−
2
−
x
)
If
f
:
{
1
,
2
,
3
,
.
.
.
}
→
{
0
,
±
1
,
±
2
,
.
.
.
}
is defined by
y
=
f
(
x
)
=
{
x
2
if x is even
−
(
x
−
1
)
2
,
if x is odd
, then
f
−
1
(
100
)
is
Report Question
0%
Function is not invertible as it is not onto
0%
199
0%
201
0%
200
Explanation
Since
100
is even
f
−
1
(
x
)
=
2
x
Hence
f
−
1
(
100
)
=
200
If
f
(
y
)
=
y
√
1
−
y
2
;
g
(
y
)
=
y
√
1
+
y
2
then
(
f
o
g
)
y
is equal to
Report Question
0%
y
√
1
−
y
2
0%
y
√
1
+
y
2
0%
y
0%
2
f
(
x
)
Explanation
Given
f
(
y
)
=
y
√
1
−
y
2
and
g
(
y
)
=
y
√
1
+
y
2
∴
(
f
o
g
)
y
=
f
(
g
(
y
)
)
=
y
√
1
+
y
2
√
1
−
y
2
1
+
y
2
=
y
If
f
(
x
)
=
(
x
−
1
)
+
(
x
+
1
)
and
g
(
x
)
=
f
{
f
(
x
)
}
then
g
′
(
3
)
Report Question
0%
equals
1
0%
equals
0
0%
equals
3
0%
equals
4
Explanation
Simplifying,
f
(
x
)
we get
f
(
x
)
=
2
x
Hence
f
(
f
(
x
)
)
=
2
(
f
(
x
)
)
=
2
(
2
x
)
=
4
x
Hence
g
(
x
)
=
f
(
f
(
x
)
)
=
4
x
Thus
g
′
(
x
)
=
4
Hence
g
′
(
3
)
=
4
.
If
f
(
x
)
=
x
+
tan
x
and
g
−
1
=
f
then
g
′
(
x
)
equals
Report Question
0%
1
2
+
[
g
(
x
)
+
x
]
2
0%
1
1
+
[
g
(
x
)
−
x
]
2
0%
1
2
+
[
g
(
x
)
−
x
]
2
0%
1
2
−
[
g
(
x
)
−
x
]
2
Explanation
f
(
x
)
=
x
+
tan
x
⇢
(
i
)
g
−
1
(
x
)
=
f
(
x
)
⇢
(
i
i
)
f
(
g
(
x
)
)
=
g
(
x
)
+
tan
g
(
x
)
(
f
r
o
m
e
q
u
a
t
i
o
n
(
i
)
)
g
−
1
(
g
(
x
)
)
=
g
(
x
)
+
tan
g
(
x
)
(
f
r
o
m
e
q
u
a
t
i
o
n
(
i
i
)
)
x
=
g
(
x
)
+
tan
g
(
x
)
⇢
(
i
i
i
)
(
∵
g
−
1
(
g
(
x
)
)
=
x
)
Differentiating the above equation w.r.t x,
1
=
g
′
(
x
)
+
(
sec
2
g
(
x
)
)
g
′
(
x
)
g
′
(
x
)
=
1
1
+
sec
2
g
(
x
)
=
1
2
+
tan
2
g
(
x
)
(
∵
sec
2
g
(
x
)
=
1
+
tan
2
g
(
x
)
)
f
r
o
m
e
q
n
(
i
i
i
)
,
tan
g
(
x
)
=
x
−
g
(
x
)
∴
g
′
(
x
)
=
1
2
+
(
x
−
g
(
x
)
)
2
Let
f
:
[
4
,
∞
)
→
[
4
,
∞
)
be a function defined by
f
(
x
)
=
5
x
(
x
−
4
)
, then
f
−
1
(
x
)
is
Report Question
0%
2
−
√
4
+
log
5
x
0%
2
+
√
4
+
log
5
x
0%
(
1
5
)
x
(
x
−
4
)
0%
None of these
Explanation
Let
y
=
5
x
(
x
−
4
)
⇒
x
(
x
−
4
)
=
log
5
y
⇒
x
2
−
4
x
−
log
5
y
=
0
⇒
x
=
4
±
√
16
+
4
log
5
y
2
=
(
2
±
√
4
+
log
5
y
)
But
x
≥
4
, so
x
=
(
2
+
√
4
+
log
5
y
)
∴
f
−
1
(
y
)
=
2
+
√
4
+
log
5
y
∴
f
−
1
(
x
)
=
2
+
√
4
+
log
5
x
Report Question
0%
Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
0%
Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
0%
Assertion is correct but Reason is incorrect
0%
Assertion is incorrect but Reason is correct
Explanation
For Onto function
codomain
=
[
0
,
π
2
)
=
Range
Which is possiable where
x
2
+
x
+
a
≥
0
Now using fact
f
(
x
)
≥
0
⇒
D
≤
0
(
A
=
1
=
b
)
a
n
d
C
=
a
⇒
1
−
4
a
≤
0
⇒
a
≥
1
4
∴
Assertion is false, Reason is true
Let
f
:
N
→
Y
be a function defined as
f
(
x
)
=
4
x
+
3
where
Y
=
{
y
∈
N
:
y
=
4
x
+
3
}
for some
x
∈
N
such that
f
is invertible then its inverse is
Report Question
0%
g
(
y
)
=
4
+
y
+
3
4
0%
g
(
y
)
=
2
y
−
3
4
0%
g
(
y
)
=
3
y
+
4
3
0%
g
(
y
)
=
y
−
3
4
Explanation
Let
y
=
f
(
x
)
⇒
x
=
f
−
1
(
y
)
........(A)
∴
y
=
4
x
+
3
⇒
4
x
=
y
−
3
⇒
x
=
y
−
3
4
⇒
f
−
1
(
y
)
=
y
−
3
4
.......(using A)
⇒
g
(
y
)
=
y
−
3
4
If
f
(
x
)
=
{
x
2
x
≥
0
x
x
<
0
then
(
f
o
f
)
(
x
)
is given by
Report Question
0%
x
2
for
x
≥
0
and
x
for
x
<
0
0%
x
4
for
x
≥
0
and
x
2
for
x
<
0
0%
x
4
for
x
≥
0
and
−
x
2
for
x
<
0
0%
x
4
for
x
≥
0
and
x
for
x
<
0
Explanation
For
x
≥
0
,we have
f
∘
f
(
x
)
=
(
x
2
)
2
=
(
x
4
)
For
x
<
0
,we have
f
∘
f
(
x
)
=
x
If
f
(
x
)
=
3
x
+
2
5
x
−
3
then
Report Question
0%
f
−
1
(
x
)
=
−
f
(
x
)
0%
f
−
1
(
x
)
=
f
(
x
)
0%
f
o
(
f
(
x
)
)
=
−
x
0%
f
−
1
(
x
)
=
−
1
19
f
(
x
)
Explanation
Let
y
=
3
x
+
2
5
x
−
3
⇒
x
=
3
y
+
2
5
y
−
3
=
f
−
1
(
y
)
∴
f
−
1
(
x
)
=
3
x
+
2
5
x
−
3
=
f
(
x
)
Let
f
:
R
→
R
be defined as
f
(
x
)
=
x
2
+
5
x
+
9
then
f
−
1
(
8
)
equals to
Report Question
0%
{
−
5
+
√
20
2
,
−
5
−
√
21
2
}
0%
{
−
5
+
√
21
2
,
−
5
−
√
21
2
}
0%
{
5
−
√
21
2
,
21
−
√
5
2
}
0%
Does not exist.
Explanation
Let
f
−
1
(
8
)
=
x
,
then
f
(
x
)
=
8
⟹
x
2
+
5
x
+
9
=
8
⟹
x
2
+
5
x
+
1
=
0
⇒
x
=
−
5
±
√
25
−
4
2
x
=
−
5
+
√
21
2
,
−
5
−
√
21
2
∈
R
Hence
f
−
1
(
8
)
=
{
−
5
+
√
21
2
,
−
5
−
√
21
2
}
Which of the following functions have inverse defined on the ranges
Report Question
0%
f
(
x
)
=
x
2
,
x
∈
R
0%
f
(
x
)
=
x
3
,
x
∈
R
0%
f
(
x
)
=
e
x
,
x
∈
R
0%
f
(
x
)
=
sin
x
,
0
<
x
<
2
π
Explanation
We know that only one-one onto functions are invertible.
In (A) it is not one-one and hence not invertible.
In (B) and (C)both are one-one onto and both are invertible.
In (D) Since
f
(
π
4
)
=
f
(
3
π
4
)
=
1
√
2
∴
(D) is not invertible.
Let f(x)=tan x, x
ϵ
[
−
π
2
,
π
2
]
and
g
(
x
)
=
√
1
−
x
2
Determine
g
o
f
(
1
)
.
Report Question
0%
1
0%
0
0%
-1
0%
not defined
Find
ϕ
[
Ψ
(
x
)
]
and
Ψ
[
ϕ
(
x
)
]
if
ϕ
(
x
)
=
x
2
+
1
and
Ψ
(
x
)
=
3
x
.
Report Question
0%
Ψ
[
ϕ
(
x
)
]
=
3
x
2
+
1
.
0%
ϕ
[
Ψ
[
x
]
]
=
3
2
x
+
1
0%
Ψ
[
ϕ
(
x
)
]
=
3
x
3
+
1
.
0%
ϕ
[
Ψ
[
x
]
]
=
3
x
+
1
Explanation
ϕ
[
Ψ
[
x
]
]
=
ϕ
(
3
x
)
=
(
3
x
)
2
+
1
=
3
2
x
+
1
and
Ψ
[
ϕ
(
x
)
]
=
Ψ
(
x
2
+
1
)
=
3
x
2
+
1
.
The inverse of the function
f
(
x
)
=
(
1
−
(
x
−
5
)
3
)
1
/
5
is
Report Question
0%
5
−
(
1
−
x
5
)
1
/
3
0%
5
+
(
1
−
x
5
)
1
/
3
0%
5
+
(
1
+
x
5
)
1
/
3
0%
5
−
(
1
+
x
5
)
1
/
3
Explanation
Let
y
=
(
1
−
(
x
−
5
)
3
)
1
5
y
5
=
1
−
(
x
−
5
)
3
(
x
−
5
)
3
=
1
−
y
5
x
−
5
=
(
1
−
y
5
)
1
3
x
=
5
+
(
1
−
y
5
)
1
3
Replacing
x
with
y
gives us
f
−
1
(
x
)
=
5
+
(
1
−
x
5
)
1
3
If
f
(
x
)
=
a
x
+
b
c
x
+
d
and
(
f
o
f
)
x
=
x
,
then d=?
Report Question
0%
a
0%
−
a
0%
b
0%
−
b
Explanation
(
f
o
f
)
x
=
x
⇒
f
[
f
(
x
)
]
=
x
or
f
[
a
x
+
b
c
x
+
d
]
=
x
or
a
[
a
x
+
b
c
x
+
d
]
+
b
c
[
a
x
+
b
c
x
+
d
]
+
d
=
x
∴
x
(
a
2
+
b
c
)
+
b
(
a
+
d
)
c
x
(
a
+
d
)
+
(
b
c
+
d
2
)
=
x
Clearly if
a
+
d
=
0
or
d
=
−
a
then in that case
L
.
H
.
S
.
=
x
(
a
2
+
b
c
)
+
0
0
+
(
b
c
+
a
2
)
=
x
∵
d
=
−
a
The inverse of the function
log
e
x
is
Report Question
0%
10
x
.
0%
e
x
0%
10
e
.
0%
x
e
.
Explanation
y
=
f
−
1
(
x
)
⇒
x
=
f
(
y
)
=
log
e
y
⇒
y
=
e
x
The total number of injective mappings from a set with
m
elements to a set with
n
elements,
m
≤
n
,
is
Report Question
0%
m
n
0%
n
m
0%
n
!
(
n
−
m
)
!
0%
n
!
Explanation
Let
A
=
{
a
1
,
a
2
,
a
3
.
.
.
.
.
a
m
}
and
B
=
{
b
1
,
b
2
,
b
3
.
.
.
.
.
b
n
}
where
m
≤
n
Given
f
:
A
→
B
be an injective mapping.
So, for
a
1
∈
A
, there are
n
possible choices for
f
(
a
1
)
∈
B
.
For
a
2
∈
A
, there are
(
n
−
1
)
possible choices for
f
(
a
2
)
∈
B
.
Similarly for
a
m
∈
A
, there are
(
n
−
m
−
1
)
choices for
f
(
a
m
)
∈
B
So, there are
n
(
n
−
1
)
(
n
−
2
)
.
.
.
.
.
(
n
−
m
−
1
)
=
n
!
(
n
−
m
)
!
injective mapping from
A
to
B
.
If
A
=
{
a
,
b
,
c
,
d
}
,
B
=
{
1
,
2
,
3
}
find whether or not the following sets of ordered pairs are relations from
A
to
B
or not.
R
1
=
{
(
a
,
1
)
,
(
a
,
3
)
}
R
2
=
{
(
a
,
1
)
,
(
c
,
2
)
,
(
d
,
1
)
}
R
3
=
{
(
a
,
1
)
,
(
b
,
2
)
,
(
3
,
c
)
}
.
Report Question
0%
R
1
R
2
are relations but
R
3
is not a relation.
0%
R
1
R
3
are relations but
R
2
is not a relation.
0%
All are relations
0%
none of these
Explanation
Given,
A
=
{
a
,
b
,
c
,
d
}
,
B
=
{
1
,
2
,
3
}
and
R
1
=
{
(
a
,
1
)
,
(
a
,
3
)
}
R
2
=
{
(
a
,
1
)
,
(
c
,
2
)
,
(
d
,
1
)
}
R
3
=
{
(
a
,
1
)
,
(
b
,
2
)
,
(
3
,
c
)
}
.
We know that every relation from
A
to
B
will be a subset of
A
×
B
.
Thus, both
R
1
and
R
2
are subsets of
A
×
B
and hence are relations but
R
3
is not a relation because
R
3
is not a subset of
A
×
B
because the element
(
3
,
c
)
∉
(
A
×
B
)
.
It belongs to
B
×
A
.
Are the following sets of ordered pairs functions? If so, examine whether the mapping is surjective or injective :
{(x, y): x is a person, y is the mother of x}
Report Question
0%
injective (one- one ) and surjective (into)
0%
injective (one- one ) and not surjective (into)
0%
not injective (one- one ) and surjective (into)
0%
not injective (one- one ) and not surjective (into)
Explanation
We have {(x, y) : x is a person, y is the mother of x}. Clearly each person 'x' has only one biological mother. So above set of ordered pair is a function. Now more than one person may have same mother. So function is many-one and surjective.
Given
f
(
x
)
=
log
(
1
+
x
1
−
x
)
and
g
(
x
)
=
3
x
+
x
3
1
+
3
x
2
,
f
o
g
(
x
)
equals
Report Question
0%
−
f
(
x
)
0%
3
f
(
x
)
0%
[
f
(
x
)
]
3
0%
none of these
Explanation
Given
f
(
x
)
=
log
(
1
+
x
1
−
x
)
and
g
(
x
)
=
3
x
+
x
3
1
+
3
x
2
∴
f
o
g
(
x
)
=
log
(
1
+
3
x
+
x
3
1
+
3
x
2
1
−
3
x
+
x
3
1
+
3
x
2
)
=
log
(
(
1
+
x
)
3
(
1
−
x
)
3
)
=
3
log
(
1
+
x
1
−
x
)
=
3
f
(
x
)
Let
R
be a relation from a set
A
to a set
B
,then
Report Question
0%
R
=
A
∪
B
0%
R
=
A
∩
B
0%
R
⊆
A
×
B
0%
R
⊆
B
×
A
Explanation
If
R
is a relation from
A
to
B
then
R
is the subset of
A
×
B
because it contains all the possible mappings from
A
to
B
.
If
A
=
{
a
,
b
,
c
,
d
}
,
B
=
{
p
,
q
,
r
,
s
}
, then which of the following are relations from
A
to
B
?
Report Question
0%
R
1
=
{
(
a
,
p
)
,
(
b
,
r
)
,
(
c
,
s
)
}
0%
R
2
=
{
(
q
,
b
)
,
(
c
,
s
)
,
(
d
,
r
)
}
0%
R
3
=
{
(
a
,
p
)
,
(
a
,
q
)
,
(
d
,
p
)
,
(
c
,
r
)
,
(
b
,
r
)
}
0%
R
4
=
{
(
a
,
p
)
,
(
q
,
a
)
,
(
b
,
s
)
,
(
s
,
b
)
}
Explanation
From then definiation of Relation
Let
R
be
a
relation from
A
to
B
i.e.,
R
⊆
A
×
B
,
then
Domain of {
a
:
a
∈
A
,
(
a
,
b
)
∈
R
for some
b
∈
B
}
Range of
R
=
{
b
:
b
∈
B
,
(
a
,
b
)
∈
R
for some
a
∈
A
}.
Therefore,
(A)
R
,
=
{
(
a
,
p
)
,
(
b
,
s
)
,
(
c
,
s
)
}
is a relation as
{
a
,
b
,
c
}
⊆
A
and
{
p
,
r
,
s
}
⊆
B
.
(B)
R
2
=
{
(
q
,
b
)
,
(
c
,
s
)
,
(
d
,
r
)
}
is not a relation as
q
is not from set
A
.
(C)
R
3
=
{
(
a
,
p
)
,
(
a
,
q
)
,
(
d
,
p
)
,
(
c
,
r
)
,
(
b
,
r
)
}
is a relation as
{
a
,
d
,
c
,
b
}
⊆
A
and
{
p
,
q
,
r
}
⊆
B
.
(D)
R
4
=
{
(
a
,
p
)
,
(
q
,
a
)
,
(
b
,
s
)
,
(
s
,
b
)
}
is not a relation as
q
and
s
does not belong to set
A
.
If
f
:
R
→
R
and
g
:
R
→
R
are functions defined by
f
(
x
)
=
3
x
−
1
;
g
(
x
)
=
√
x
+
6
, then the value of
(
g
∘
f
−
1
)
(
2009
)
is
Report Question
0%
26
0%
29
0%
16
0%
15
Explanation
Given
f
(
x
)
=
3
x
−
1
,
g
(
x
)
=
√
x
+
6
Let
f
(
x
)
=
y
⇒
y
=
3
x
−
1
⇒
y
+
1
−
3
x
⇒
x
=
y
+
1
3
Now,
f
−
1
(
y
)
=
x
=
y
+
1
3
⇒
f
−
1
(
x
)
=
x
+
1
3
and
g
(
x
)
=
√
x
+
6
Consider,
(
g
∘
f
−
1
)
(
2009
)
=
g
[
f
−
1
(
2009
)
]
=
g
(
2009
+
1
3
)
=
g
(
2010
3
)
=
√
2010
3
+
6
=
√
2028
3
=
√
676
=
26
Hence, option
A
is correct.
If
X
=
{
1
,
2
,
3
,
4
,
5
}
,
Y
=
{
1
,
3
,
5
,
7
,
9
}
determine which of the following sets are mappings, relations or neither from A to B:
(i)
F
=
{
(
x
,
y
)
∵
y
=
x
+
2
,
x
∈
X
,
y
∈
Y
}
Report Question
0%
It is clearly a one-one onto mapping i.e. a bijection. It is also a relation.
0%
It is clearly a many-one onto mapping. It is also a relation.
0%
It is clearly a one-one but not onto mapping. It is also a relation.
0%
It is not a mapping but a relation
Explanation
Given def of F as
F
=
{
(
x
,
y
)
∵
y
=
x
+
2
,
x
ϵ
X
,
y
ϵ
Y
}
where
X
=
{
1
,
2
,
3
,
4
,
5
}
,
Y
=
{
1
,
3
,
5
,
7
,
9
}
So, we get
{
(
1
,
3
)
,
(
2
,
4
)
,
(
3
,
5
)
,
(
4
,
6
)
,
(
5
,
7
)
}
Since,
y
∈
Y
and in the above 4,6 do not belong to Y.
∴
we exclude the ordered pair (2,4) and (4,6)
∴
F
=
{
(
1
,
3
)
,
(
3
,
5
)
,
(
5
,
7
)
}
F is not a mapping because the elements 2,4
ϵ
X
do not have any image.
F
⊂
X
×
Y
and hence F is a relation from X to Y.
Let
f
:
[
2
,
∞
)
→
[
1
,
∞
)
defined by
f
(
x
)
=
2
x
4
−
4
x
2
and
g
:
[
π
2
,
π
]
→
A
defined by
g
(
x
)
=
sin
x
+
4
sin
x
−
2
be two invertible functions, then
f
−
1
(
x
)
is equal to
Report Question
0%
√
2
+
√
4
−
log
2
x
0%
√
2
+
√
4
+
log
2
x
0%
√
2
−
√
4
+
log
2
x
0%
None of these
Explanation
∵
f
f
−
1
(
x
)
=
x
2
(
f
−
1
(
x
)
)
4
−
4
(
f
−
1
(
x
)
)
2
=
x
⇒
(
f
−
1
(
x
)
)
4
−
4
(
f
−
1
(
x
)
)
2
=
log
2
x
=
0
∴
(
f
−
1
(
x
)
)
2
=
2
+
√
4
+
log
2
x
∴
Range of
f
−
1
(
x
)
is
(
2
,
∞
)
.
∴
f
−
1
(
x
)
=
√
2
+
√
4
+
log
2
x
If
f
0
(
x
)
=
x
(
x
+
1
)
and
f
n
+
1
=
f
0
∘
f
n
(
x
)
for
n
=
0
,
1
,
2
,
⋯
then
f
n
(
x
)
is
Report Question
0%
x
(
n
+
1
)
x
+
1
0%
f
0
(
x
)
0%
n
x
n
x
+
1
0%
x
n
x
+
1
Explanation
Given
f
0
(
x
)
=
x
(
x
+
1
)
⋯
⋯
(
1
)
Also given
f
n
+
1
=
f
0
o
f
n
for
(
n
=
0
,
1
,
2
,
⋯
)
…
(
2
)
Put
n
=
0
in eqn (2)
f
1
=
f
0
o
f
0
f
1
(
x
)
=
f
0
[
f
0
(
x
)
]
⇒
f
1
(
x
)
=
f
0
(
x
x
+
1
)
=
x
x
+
1
x
x
+
1
+
1
=
x
2
x
+
1
⇒
f
1
(
x
)
=
x
2
x
+
1
Put
n
=
1
in eqn
(
2
)
f
2
=
f
0
o
f
1
f
2
(
x
)
=
f
0
[
f
1
(
x
)
]
⇒
f
2
(
x
)
=
f
0
(
x
2
x
+
1
)
=
x
2
x
+
1
x
2
x
+
1
+
1
=
x
3
x
+
1
⇒
f
2
(
x
)
=
x
3
x
+
1
Hence,
f
n
(
x
)
=
x
(
n
+
1
)
x
+
1
Let
f
(
x
)
=
x
2
−
2
x
and
g
(
x
)
=
f
(
f
(
x
)
−
1
)
+
f
(
5
−
f
(
x
)
)
,
then
Report Question
0%
g
(
x
)
<
0
,
∀
x
∈
R
0%
g
(
x
)
<
0
for some
x
∈
R
0%
g
(
x
)
≤
0
for some
x
∈
R
0%
g
(
x
)
≥
0
,
∀
x
∈
R
Explanation
Given,
f
(
x
)
=
x
2
−
2
x
Now,
f
(
f
(
x
)
−
1
)
=
f
(
x
2
−
2
x
−
1
)
=
(
x
2
−
2
x
−
1
)
2
−
2
(
x
2
−
2
x
−
1
)
And,
f
(
5
−
f
(
x
)
)
=
f
(
5
−
x
2
+
2
x
)
=
(
5
−
x
2
+
2
x
)
2
−
2
(
5
−
x
2
+
2
x
)
Hence,
g
(
x
)
=
f
(
f
(
x
)
−
1
)
+
f
(
5
−
f
(
x
)
)
∴
g
(
x
)
=
(
x
2
−
2
x
−
1
)
2
−
2
(
x
2
−
2
x
−
1
)
+
(
5
−
x
2
+
2
x
)
2
−
2
(
5
−
x
2
+
2
x
)
⇒
g
(
x
)
=
(
x
2
−
2
x
−
1
)
2
+
(
5
−
x
2
+
2
x
)
2
−
2
(
x
2
−
2
x
−
1
+
5
−
x
2
+
2
x
)
∴
g
(
x
)
=
(
x
2
+
2
x
−
1
)
2
+
(
5
−
2
x
2
+
2
x
2
)
2
−
8
Since the first two terms are in square,
∴
it can not be negative and if x = 9 then we also get positive value.
∴
g
(
x
)
≥
0
∀
x
∈
R
∴
option D is
correct
If
f
(
x
)
=
{
2
x
+
3
x
≤
1
a
2
x
+
1
x
>
1
, then the values of
a
for which
f
(
x
)
is injective.
Report Question
0%
−
3
0%
1
0%
0
0%
none of these
Explanation
A function is called injective (one-one) if it is monontonic.
Clearly for
x
<
1
f is increasing and it's maximum values is
2
(
1
)
+
3
=
5
Hence for f to be monotonic
(
x
>
1
)
,
f
(
1
)
≥
5
⇒
a
2
(
1
)
+
1
≥
5
⇒
a
2
≥
2
⇒
a
∈
R
−
(
−
2
,
2
)
Which of the functions defined below are NOT one-one function(s)
Report Question
0%
f
(
x
)
=
5
(
x
2
+
4
)
,
(
x
∈
R
)
0%
g
(
x
)
=
2
x
+
1
x
0%
h
(
x
)
=
l
n
(
x
2
+
x
+
1
)
,
(
x
∈
R
)
0%
f
(
x
)
=
e
−
x
If
g
(
x
)
=
1
+
√
x
and
f
(
g
(
x
)
)
=
3
+
2
√
x
+
x
, then
f
(
x
)
=
Report Question
0%
1
+
2
x
2
0%
2
+
x
2
0%
1
+
x
0%
2
+
x
Explanation
We have
g
(
x
)
=
1
+
√
x
and
f
(
g
(
x
)
)
=
3
+
2
√
x
+
x
...(1)
Also,
f
(
g
(
x
)
)
=
f
(
1
+
√
x
)
...(2)
From (1) and (2), we get
f
(
1
+
√
x
)
=
3
+
2
√
x
+
x
Let
1
+
√
x
=
y
⇒
x
=
(
y
−
1
)
2
∴
f
(
y
)
=
3
+
2
(
y
−
1
)
+
(
y
−
1
)
2
=
3
+
3
y
−
2
+
y
2
−
2
y
+
1
=
2
+
y
2
∴
f
(
x
)
=
2
+
x
2
Let
X
=
{
1
,
2
,
3
,
4
}
and
Y
=
{
1
,
2
,
3
,
4
}
. Which of the following is a relation from
X
to
Y
.
Report Question
0%
R
1
=
{
(
x
,
y
)
|
y
=
2
+
x
,
x
∈
X
,
y
∈
Y
}
0%
R
2
=
{
(
1
,
1
)
,
(
2
,
1
)
,
(
3
,
3
)
,
(
4
,
3
)
,
(
5
,
5
)
}
0%
R
3
=
{
(
1
,
1
)
,
(
1
,
3
)
,
(
3
,
5
)
,
(
3
,
7
)
,
(
5
,
7
)
}
0%
R
4
=
{
(
1
,
3
)
,
(
2
,
5
)
,
(
2
,
4
)
,
(
7
,
9
)
}
Explanation
Given
X
=
{
1
,
2
,
3
,
4
}
and
Y
=
{
1
,
2
,
3
,
4
}
X
×
Y
=
{
(
1
,
1
)
,
(
1
,
2
)
,
(
1
,
3
)
,
(
1
,
4
)
,
(
2
,
1
)
,
(
2
,
2
)
,
(
2
,
3
)
,
(
2
,
4
)
(
3
,
1
)
,
(
3
,
2
)
,
(
3
,
3
)
,
(
3
,
4
)
,
(
4
,
1
)
,
(
4
,
2
)
,
(
4
,
3
)
,
(
4
,
4
)
}
Now,
R
1
=
{
(
1
,
3
)
,
(
2
,
2
)
}
Since,
R
1
⊂
X
×
Y
Hence,
R
1
is a relation from
X
to
Y
R
2
=
{
(
1
,
1
)
,
(
2
,
1
)
,
(
3
,
3
)
,
(
4
,
3
)
,
(
5
,
5
)
}
Since,
(
5
,
5
)
∈
R
2
but
∉
X
×
Y
So,
R
2
is not a relation from
X
to
Y
R
3
=
{
(
1
,
1
)
,
(
1
,
3
)
,
(
3
,
5
)
,
(
3
,
7
)
,
(
5
,
7
)
}
Since,
(
3
,
5
)
,
(
3
,
7
)
,
(
5
,
7
)
∈
R
3
but
∉
X
×
Y
So,
R
3
is not a relation from
X
to
Y
R
4
=
{
(
1
,
3
)
,
(
2
,
5
)
,
(
2
,
4
)
,
(
7
,
9
)
}
Since,
(
2
,
5
)
,
(
7
,
9
)
∈
R
4
but
∉
X
×
Y
So,
R
4
is not a relation from
X
to
Y
Find inverse
f
(
x
)
=
log
e
(
x
+
√
x
2
+
1
)
Report Question
0%
sinh
(
x
)
0%
cosh
(
x
)
0%
tanh
(
x
)
0%
coth
(
x
)
Explanation
y
=
log
(
x
+
√
x
2
+
1
)
⇒
e
y
=
x
+
√
x
2
+
1
⇒
e
y
−
x
=
√
x
2
+
1
⇒
x
2
−
2
x
e
y
+
e
2
y
=
x
2
+
1
⇒
e
2
y
=
1
+
2
x
e
y
⇒
2
x
=
e
2
y
−
1
e
y
⇒
x
=
e
y
−
e
−
y
2
Replacing x with y
f
−
1
(
x
)
=
e
x
−
e
−
x
2
=
sinh
(
x
)
Let f : {x,y,z}
→
{a,b,c} be a one-one function. It is known that only one of the following statment is true, and only one such function exists :
find the function f (as ordered pair).
(i) f(x)
≠
b
(i) f(y) = b
(ii) f(z)
≠
a
Report Question
0%
{(x,b), (y,a), (z,c)}
0%
{(x,a), (y,b), (z,c)}
0%
{(x,b), (y,c), (z,a)}
0%
{(x,c), (y,a), (z,b)}
Explanation
When (i) is true, then
f
(
x
)
≠
b
,
f
(
y
)
≠
b
,
f
(
z
)
=
a
,
b
,
c
⇒
Two ordered pair function is possible
f
(
x
)
=
a
,
f
(
y
)
=
c
,
f
(
z
)
=
b
or
f
(
x
)
=
c
,
f
(
y
)
=
a
,
f
(
z
)
=
b
But given
f
is one-one and only one such function is possible. Hence (i) can't be true.
When (ii) is true, then
f
(
y
)
=
b
,
f
(
z
)
=
c
,
f
(
x
)
=
a
⇒
f
(
x
)
=
a
,
f
(
y
)
=
b
,
f
(
z
)
=
c
Clearly if (ii) is true then it is satisfying every condition.
Hence ordered pair of
f
is
{
(
x
,
a
)
,
(
y
,
b
)
,
(
z
,
c
)
}
Suppose f and g both are linear function with
f
(
x
)
=
−
2
x
+
1
and
f
(
g
(
x
)
)
=
6
x
−
7
then slope of line
y
=
g
(
x
)
is
Report Question
0%
3
0%
−
3
0%
6
0%
−
2
Explanation
Given,
f
(
x
)
=
−
2
x
+
1
∴
f
(
g
(
x
)
)
=
−
2
g
(
x
)
+
1
=
6
x
−
7
⇒
g
(
x
)
=
−
3
x
+
4
⇒
g
′
(
x
)
=
−
3
Hence slope of
g
(
x
)
is
−
3
from the given statement
N
denotes the natural number and
W
denotes the whole number, so which statement in the following is correct
Report Question
0%
N=W
0%
N
⊂
W
0%
W
⊂
N
0%
N
≅
W
Explanation
Natural numbers are naturally occurring counts of an object
1
,
2
,
3
,
4
,
…
forming an infinite list in which the first number is
1
and every next number is equal to the preceding number
+
1.
Whole number include the set of all Natural numbers and also
0.
Let
N
and
W
elements of natural and whole numbers.
N
=
{
1
,
2
,
3
,
4
,
.
.
.
.
∞
}
W
=
{
0
,
1
,
2
,
3
,
4
,
.
.
.
∞
}
So, here we can say
N
is subset of
W
.
∴
N
⊂
W
is correct statement.
If
f
(
x
)
=
{
x
+
1
,
i
f
x
≤
1
5
−
x
2
i
f
x
>
1
,
g
(
x
)
=
{
x
i
f
x
≤
1
2
−
x
i
f
x
>
1
and
x
∈
(
1
,
2
)
, then
g
(
f
(
x
)
)
is equal to
Report Question
0%
x
2
+
3
0%
x
2
−
3
0%
5
−
x
2
0%
1
−
x
Explanation
x
ϵ
(
1
,
2
)
Hence for x >1,
f
(
x
)
=
5
−
x
2
and
f
(
x
)
ϵ
(
1
,
4
)
f
(
x
)
>
1
g
(
f
(
x
)
)
=
2
−
f
(
x
)
=
2
−
5
+
x
2
=
x
2
−
3
If
g
(
x
)
=
2
x
+
1
and
h
(
x
)
=
4
x
2
+
4
x
+
7
, find a function
f
such that
f
o
g
=
h
Report Question
0%
f
(
x
)
=
x
3
−
6
0%
f
(
x
)
=
x
2
+
6
0%
f
(
x
)
=
x
2
−
6
0%
f
(
x
)
=
(
2
x
+
1
)
2
+
6
Explanation
f
(
g
(
x
)
)
=
h
=
4
x
2
+
4
x
+
7
=
(
2
x
+
1
)
2
+
6
=
(
g
(
x
)
)
2
+
6
⇒
f
(
x
)
=
x
2
+
6
Let
X
=
{
1
,
2
,
3
,
4
}
and
Y
=
{
1
,
3
,
5
,
7
,
9
}
. Which of the following is relations from
X
to
Y
Report Question
0%
R
1
=
{
(
x
,
y
)
|
y
=
2
x
+
1
,
x
∈
X
,
y
∈
Y
}
0%
R
2
=
{
(
1
,
1
)
,
(
2
,
1
)
,
(
3
,
3
)
,
(
4
,
3
)
,
(
5
,
5
)
}
0%
R
3
=
{
(
1
,
1
)
,
(
1
,
3
)
,
(
3
,
5
)
,
(
3
,
7
)
,
(
5
,
7
)
}
0%
R
4
=
{
(
1
,
3
)
,
(
2
,
5
)
,
(
2
,
4
)
,
(
7
,
9
)
}
Explanation
We have
X
=
{
1
,
2
,
3
,
4
}
and
Y
=
{
1
,
3
,
5
,
7
,
9
}
.
X
×
Y
=
{
(
1
,
1
)
,
(
1
,
3
)
,
(
1
,
5
)
,
(
1
,
7
)
,
(
1
,
9
)
,
(
2
,
1
)
,
(
2
,
3
)
,
(
2
,
5
)
,
(
2
,
7
)
,
(
2
,
9
)
,
(
3
,
1
)
,
(
3
,
3
)
,
(
3
,
5
)
,
(
3
,
7
)
,
(
3
,
9
)
,
(
4
,
1
)
,
(
4
,
3
)
,
(
4
,
5
)
,
(
4
,
7
)
,
(
4
,
9
)
}
Let's take option A,
R
1
=
{
(
x
,
y
)
|
y
=
2
x
+
1
,
x
∈
X
,
y
∈
Y
}
R
1
=
{
(
1
,
3
)
,
(
2
,
5
)
,
(
3
,
7
)
,
(
4
,
9
)
}
Since,
R
1
⊆
X
×
Y
So,
R
1
is a relation from
X
to
Y
Clearly,
R
2
is not a relation from
X
to
Y
as
(
5
,
5
)
∉
X
×
Y
Similarly,
R
3
is not a relation from
X
to
Y
as
(
5
,
7
)
∉
X
×
Y
In the same manner,
R
4
is also not a relation from
X
to
Y
as
(
7
,
9
)
∉
X
×
Y
Which of the following are two distinct linear functions which map the interval
[
−
1
,
1
]
onto
[
0
,
2
]
Report Question
0%
f
(
x
)
=
1
+
x
or
1
−
x
0%
f
(
x
)
=
1
+
2
x
or
1
−
x
0%
f
(
x
)
=
1
+
x
or
1
−
2
x
0%
f
(
x
)
=
1
+
x
or
2
−
x
Explanation
Out of two linear functions one will be increasing and other will be decreasing.
Let
f
(
x
)
=
a
x
+
b
For increasing:
f
(
−
1
)
=
0
=>
b
−
a
=
0
⇒
b
=
a
and
f
(
1
)
=
2
⇒
a
+
b
=
2
⇒
a
=
b
=
1
∴
f
(
x
)
=
1
+
x
For decreasing:
f
(
−
1
)
=
2
=>
b
−
a
=
2
and
f
(
1
)
=
0
⇒
a
+
b
=
2
⇒
b
=
1
,
a
=
−
1
∴
f
(
x
)
=
1
−
x
If
f
(
x
)
=
ln
1
+
x
1
−
x
and
g
(
x
)
=
3
x
+
x
3
1
+
3
x
2
, then
f
[
g
(
x
)
]
equals.
Report Question
0%
f
(
x
)
0%
[
f
(
x
)
]
3
0%
3
f
(
x
)
0%
f
(
x
)
2
Explanation
Given
f
(
x
)
=
ln
1
+
x
1
−
x
and
g
(
x
)
=
3
x
+
x
3
1
+
3
x
2
then
f
[
g
(
x
)
]
=
ln
1
+
3
x
+
x
3
1
+
3
x
2
1
−
3
x
+
x
3
1
+
3
x
2
=
ln
1
+
3
x
2
+
3
x
+
x
3
1
+
3
x
2
−
3
x
−
x
3
=
ln
[
1
+
x
1
−
x
]
3
=
3
ln
1
+
x
1
−
x
⇒
f
[
g
(
x
)
]
=
3
f
(
x
)
Hence, option C.
Let
f
(
x
)
=
e
3
x
,
g
(
x
)
=
log
e
x
,
x
>
0
, then
f
o
g
(
x
)
is
Report Question
0%
3
x
0%
x
3
0%
log
10
3
x
0%
log
3
x
Explanation
Given
f
(
x
)
=
e
3
x
,
g
(
x
)
=
log
e
x
,
x
>
0
f
o
g
(
x
)
=
f
(
log
e
x
)
=
e
3
log
e
x
=
x
3
Hence, option B.
f
(
x
)
>
x
;
∀
x
ϵ
R
.
The equation
f
(
f
(
x
)
)
−
x
=
0
has
Report Question
0%
Atleast one real root
0%
More than one real root
0%
No real root if f(x) is a polynomial & one real root if f(x) is not a polynomial
0%
No real root at all
Explanation
Given
f
(
x
)
>
x
∀
x
ϵ
R
Hence,
f
(
x
)
−
x
has no real roots, because
f
(
x
)
−
x
>
0
Since,
x
ϵ
R
⟹
f
(
x
)
ϵ
R
f
(
f
(
x
)
)
>
x
⟹
f
(
f
(
x
)
)
−
x
>
0
Hence it will have no real root.
If
f
:
R
→
R
,
f
(
x
)
=
(
x
+
1
)
2
and
g
:
R
→
R
,
g
(
x
)
=
x
2
+
1
then
(
f
o
g
)
(
3
)
is equal to
Report Question
0%
121
0%
144
0%
112
0%
11
Explanation
Given,
f
:
R
→
R
,
f
(
x
)
=
(
x
+
1
)
2
and
g
:
R
→
R
,
g
(
x
)
=
x
2
+
1
g
(
3
)
=
3
2
+
1
=
10
f
(
10
)
=
(
10
+
1
)
2
=
121
∴
f
o
g
(
3
)
=
f
(
g
(
3
)
)
=
f
(
10
)
=
121
Hence, option A.
If
f
(
x
)
=
√
|
x
−
1
|
and
g
(
x
)
=
sin
x
, then
(
f
o
g
)
(
x
)
equals
Report Question
0%
sin
√
|
x
−
1
|
0%
|
sin
x
2
−
cos
x
2
|
0%
|
sin
x
+
cos
x
|
0%
|
sin
x
2
+
cos
x
2
|
Explanation
f
o
g
(
x
)
=
f
(
g
(
x
)
)
=
√
|
sin
x
−
1
|
=
√
|
1
−
cos
(
π
2
−
x
)
|
=
√
2
|
sin
(
π
4
−
x
2
)
|
=
|
sin
x
2
−
cos
x
2
|
If
f
(
x
)
=
log
x
,
g
(
x
)
=
x
3
, then
f
[
g
(
a
)
]
+
f
[
g
(
b
)
]
equals
Report Question
0%
f
[
g
(
a
)
+
g
(
b
)
]
0%
3
f
(
a
b
)
0%
g
[
f
(
a
b
)
]
0%
g
[
f
(
a
)
+
f
(
b
)
]
Explanation
We have
f
(
x
)
=
log
x
g
(
x
)
=
x
3
g
(
a
)
=
a
3
f
(
g
(
a
)
)
=
log
(
a
3
)
f
(
g
(
a
)
)
=
3
log
a
Similarly,
f
(
g
(
b
)
)
=
3
log
b
⇒
f
(
g
(
a
)
)
+
f
(
g
(
b
)
)
=
3
log
a
+
3
log
b
⇒
f
(
g
(
a
)
)
+
f
(
g
(
b
)
)
=
3
log
a
b
⇒
f
(
g
(
a
)
)
+
f
(
g
(
b
)
)
=
3
f
(
a
b
)
If
f
(
x
)
=
x
3
and
g
(
x
)
=
s
i
n
2
x
, then
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0%
g
[
f
(
1
)
]
=
1
0%
f
(
g
(
π
/
12
)
=
1
/
8
0%
g
f
(
2
)
=
sin
2
0%
none of these
Explanation
Given,
f
(
x
)
=
x
3
and
g
(
x
)
=
sin
2
x
Clearly,
f
(
1
)
=
1
⇒
g
[
f
(
1
)
]
=
sin
2
g
(
π
12
)
=
1
2
⇒
f
[
g
(
π
12
)
]
=
1
8
and,
f
(
2
)
=
8
⇒
g
[
f
(
2
)
]
=
sin
16
So, the correct option is (B).
If
f
(
x
)
=
(
a
x
n
)
1
/
n
,
where
n
∈
N
, then
f
{
f
(
x
)
}
equals
Report Question
0%
0
0%
x
0%
x
n
0%
none of these
Explanation
We have,
f
(
x
)
=
(
a
x
n
)
1
/
n
=
a
1
/
n
x
=
k
x
where
k
=
a
1
/
n
∴
f
{
f
(
x
)
}
=
k
f
(
x
)
=
k
2
x
=
a
2
/
n
x
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Practice Class 12 Commerce Maths Quiz Questions and Answers
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