If two of the four expressions a + b , b +…

If two of the four expressions a + b , b + 7b, a - b, and 7a - b are chosen at random, what is the probability that their product will be of the form of a^2-(xb)^2, where x is an integer?

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #4334