12(x+y)^2+11(x^2-y^2)+2(x-y)^2 用十字相乘法
问题描述:
12(x+y)^2+11(x^2-y^2)+2(x-y)^2 用十字相乘法
答
原式=12(x+y)²+11(x+y)(x-y)+2(x-y)²
3 2
×
4 1
所以原式=[3(x+y)+2(x-y)][4(x+y)+(x-y)]
=(5x+y)(5x+3y)