Question:
If $P\left(\frac{a}{2}, 4\right)$ is the midpoint of the line segment joining the points $A(-6,5)$ and $B(-2,3)$ then the value of $a$ is
(a) $-8$
(b) 3
(c) $-4$
(d) 4
Solution:
The point $P\left(\frac{a}{2}, 4\right)$ is the midpoint of the line segment joining the points $A(-6,5)$ and $B(-2,3)$. So
$\frac{a}{2}=\frac{-6-2}{2}$
$\Rightarrow \frac{a}{2}=-4$
$\Rightarrow a=-8$
Hence, the correct answer is option (a).