: (x + y) (x + y) ^ - (x + y) (2x + y) ^ 완전 제곱 으로 계산

: (x + y) (x + y) ^ - (x + y) (2x + y) ^ 완전 제곱 으로 계산

(x + y) (x + y) ^ 2 - (x + y) (2x + y) ^ 2
= (x + y) [(x + y) ^ 2 - (2x + y) ^ 2]
= (x + y) [(x + y + 2x + y) (x + y - 2x - y)]
= (x + y) [- x (3x + 2y)]
= - x (x + y) (3x + 2 y)