Explanation
$$r = - \hat i + \hat j + \hat k + p (3\hat i - 2\hat k)$$
$$r = - \hat i + \hat j + \hat k + p (3\hat i + 2\hat k)$$
$$r = - \hat i + \hat j + \hat k + p (-3\hat i + 2\hat k)$$
$$r = -\hat i + \hat j + \hat k + p (3\hat i + 2 \hat j )$$
Let the plane $$ax+by + cz + d =0$$ divides the lines joining $$(x_1, y_1, z_1)$$ and $$(x_2, y_2, z_2)$$ in the ratio $$k:1$$ as shown in figure.
$$\therefore $$Coordinates of $$\displaystyle P \left ( \dfrac{kx_2 + x_1}{k + 1}, \dfrac{ky_2 + y_1}{k+1}, \dfrac{kz_2 + z_1}{k+1} \right )$$ must satisfy $$ax + by + ca + d = 0$$
i.e., $$\displaystyle \left ( a \dfrac{kx_2 + x_1}{k + 1} \right ) + b\left ( \dfrac{ky_2 + y_1}{k + 1} \right) + c \left ( \dfrac{kz_2 + z_1}{k + 1} \right) + d = 0$$
$$\Rightarrow a(kx_2 + x_1) + b (ky_2 + y_1) + c (kz_2 + z_1) + c(kz_2 + z_1) + d (k + 1)= 0$$
$$\Rightarrow k (ax_2 + by_2 + cz_2 + d) + (ax_1 + by_1 + cz_1 + d)= 0$$
$$\Rightarrow \displaystyle k = - \dfrac{(ax_1 + by_1 + cz_1 + d)}{(ax_2 + by_2 + cz_2 + d)}$$
Hence, option A is correct.
$$2x + 3y + 5z = 1$$ divides $$(1, 0, -3)$$ and $$(1, -5, 7)$$ in the ratio of $$k : 1$$ at point $$P$$.
Then, $$\displaystyle P \left ( \displaystyle \dfrac{k + 1}{k + 1} , \displaystyle \dfrac{-5k}{k + 1}, \displaystyle \dfrac{7k - 3}{k + 1} \right )$$ which must satisfy $$2x + 3y + 5z = 1$$
$$\Rightarrow 2 \left ( \displaystyle \dfrac{k + 1}{k + 1} \right ) + 3 \left ( \displaystyle \dfrac{-5k}{k + 1} \right ) + 5 \left (\displaystyle \dfrac{7k - 3}{k + 1} \right ) = 1$$
$$\Rightarrow 2k + 2 - 15 k + 35 k - 15 = k + 1$$
$$\Rightarrow 21 k = 14$$
$$\Rightarrow k = \displaystyle \dfrac{2}{3}$$
$$\therefore 2x + 3y + 5z = 1$$ divides $$(1, 0, -3)$$ and $$(1, -5, 7)$$ in the ratio of $$2 : 3$$.
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