（x的平方-4Y的平方）-（x+2y)2,（x的平方-y的平方）（x+y)-(x-y)的立方

Question

（x的平方-4Y的平方）-（x+2y) 2,（x的平方-y的平方）（x+y)-(x-y)的立方

Answer 1

（x的平方-4Y的平方）-（x+2y) ²
=(x+2y)(x-2y)-(x+2y)²
=(x+2y)(x-2y-x-2y)
=-4y(x+2y)
（x的平方-y的平方）（x+y)-(x-y)的立方
=(x+y)(x-y)（x+y)-(x-y)的立方
=(x-y)[(x+y)²-(x-y)²]
=(x-y)(x+y+x-y)(x+y-x+y)
=4xy(x-y)