The ratio in which the line segment joining P (x1, y1) and Q (x2, y2) is divided by x-axis is
(a) y1 : y2
(b) −y1 : y2
(c) x1 : x2
(d) −x1 : x2
Let $C(x, 0)$ be the point of intersection of $x$-axis with the line segment joining $P\left(x_{1}, y_{1}\right)$ and $Q\left(x_{2}, y_{2}\right)$ which divides the line segment $P Q$ in the ratio $\lambda: 1$.
Now according to the section formula if point a point $\mathrm{P}$ divides a line segment joining $\mathrm{A}\left(x_{1}, y_{1}\right)$ and $\mathrm{B}\left(x_{2}, y_{2}\right)$ in the ratio m:n internally than,
$\mathrm{P}(x, y)=\left(\frac{m x_{1}+m v_{2}}{m+n}, \frac{m y_{1}+m y_{2}}{m+n}\right)$
Now we will use section formula as,
$(x, 0)=\left(\frac{\lambda x_{2}+x_{1}}{\lambda+1}, \frac{\lambda y_{2}+y_{1}}{\lambda+1}\right)$
Now equate the y component on both the sides,
$\frac{\lambda y_{2}+y_{1}}{\lambda+1}=0$
On further simplification,
$\lambda=-\frac{y_{1}}{y_{2}}$
So the answer is (b)