Answer to Question #232891 in Algebra for Tunde

Question

Prove that (-a)^2 is equal to a^2. Use this theorem (-a)(-b)=ab

Answer 1

The product of two negative numbers or terms is positive:

$$(-a)(-b)=ab$$

Then

$$(-a)^2=(-a)(-a)=a(a)=a^2$$

Therefore

$$(-a)^2=a^2$$