Explanation:
(A) : Given,
The coordinate of end points of line are
\(\mathrm{A}(3,1,-5)\) and \(\mathrm{B}(1,4,-6)\)
Let the yz plane divide the line in \(\mathrm{k}: 1\) ratio.
Let the coordinate of points \(c\) is \((x, y, z)\)
We know that,
In \(\mathrm{yz}-\) Plane, \(\mathrm{x}=0\)
\(\therefore(\mathrm{x}, \mathrm{y}, \mathrm{z})=\left(\frac{1 \times \mathrm{k}+3}{\mathrm{k}+1}, \frac{4 \mathrm{k}+1}{\mathrm{k}+1}, \frac{-6 \mathrm{k}-5}{\mathrm{k}+1}\right)\)
\((0, \mathrm{y}, \mathrm{z})=\left(\frac{\mathrm{k}+3}{\mathrm{k}+1}, \frac{4 \mathrm{k}+1}{\mathrm{k}+1}, \frac{-6 \mathrm{k}-5}{\mathrm{k}+1}\right)\)
\(\therefore \quad \frac{\mathrm{k}+3}{\mathrm{k}+1}=0\)
\(\mathrm{k}+3=0\)
\(\mathrm{k}=-3\)
\(\therefore\) The ratio is \(-3: 1\)