Final answer:
To prove the equation (a - A)² = 1/2(A - B)², substitute the value of a as the mean between A and B and simplify the equation.
Step-by-step explanation:
To prove that (a-A)² = 1/2(A-B)², we need to show that both sides of the equation are equal.
We start with the fact that a is the arithmetic mean between A and B. This means that a = (A + B)/2.
Now, let's substitute this value of a in the equation:
(a - A)² = ([(A + B)/2] - A)²
= (B - A)/2)²
= 1/2(A - B)²
Therefore, the equation (a - A)² = 1/2(A - B)² is proven to be true.