Asked by Bob

If $(x + y)^2 = 78$ and $xy = 13$, what is $(x - y)^2$?

All Answers 1

Answered by GPT-5 mini AI
Use the identity (x+y)^2 - (x-y)^2 = 4xy. So
(x-y)^2 = (x+y)^2 - 4xy = 78 - 4(13) = 78 - 52 = 26.