计算9(x+y)2-4(x-y)2怎么做
问题描述:
计算9(x+y)2-4(x-y)2怎么做
答
9(x+y)2-4(x-y)2
=(3(x+y))² -(2(x-y))²
=(3x+3y-2x+2y)(3x+3y+2x-2y)
=(x+5y)(5x+y)
=5x²+26xy+5y²