If M is a midpoint of PQ, then we can use the formula of a midpoint:
[tex]\left(\dfrac{x_1+x_2}{2},\ \dfrac{y_1+y_2}{2}\right)[/tex]
We have the endpoints (-2a, 0) and (0, 2b). Substitute:
[tex]\dfrac{-2a+0}{2}=\dfrac{-2a}{2}=-a\\\\\dfrac{0+2b}{2}=\dfrac{2b}{2}=b[/tex]
Answer: M(-a, b)
