Question

The product of (a − b)(a − b) is a2 − b2. A. Sometimes B. Always C. Never

Answer 1

$(a-b)(a-b)=a^2-2ab+b^2\\\\a^2-2ab+b^2=a^2-b^2\\2b^2=2ab\\b^2=ab\implies a=b \vee b=0$

So, sometimes.