What is the common denominator of 1 over A plus 1 over b in the complex fraction the fraction with numerator 1 over A minus 1 over b and denominator 1 over A plus 1 over b ?

The terms 1/A and 1/b have denominators A and b. Their least common denominator is the product Ab, so each fraction can be rewritten with denominator Ab: 1/A = b/(Ab) and 1/b = A/(Ab). Therefore, the common denominator is Ab, choice A.

AI-written and checked against the verified answer.