5a (x - y) ^ 2 + 10a (y - x) ^ 3

5a (x - y) ^ 2 + 10a (y - x) ^ 3

5a (x - y) ^ 2 + 10a (y - x) ^ 3
= 5a (x - y) ^ 2 [1 + 2 (y - x)]
= 5a (x - y) ^ 2 (2y - 2x + 1)