If two of the four expressions x+y, x+5y, x-y, 5x+y are chosen…

If two of the four expressions x+y, x+5y, x-y, 5x+y are chosen at random, what is the probability that their product will be of the form of x^2 - (by)^2, where b is an integer?

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #64814