To find the midpoint of the two points (x₁ ,y₁) and (x₂, y₂) we need to use the formula:
So to find the midpoint of E (a,a) and F (3a, a), let's plug it in to the formula:
Simplify the numerator:
Simplifying the fractions more:
So the midpoint of EF is (2a,a).
Your answer of (a,a) would be wrong.