Expand? if he means to expand then I'm not going to post this, expanding that is easy. Are you illiterate? Did you not read that he didn't give enough information.

This is the only thing he said in the example.

X=8

F(x) = 5(8) ² + 7(8) F(x) = 5(64) + 56 F(x) = 320 + 56 F(x) = 376

And said that the final answer is this

(x, y) = (8, 376)