计算题 多项式乘以多项式

题目

计算题 多项式乘以多项式
3(-4x+y)(x-y)+2(3x-2y)(x+3y) x=-2 y=1
=(-12x+3y)(x-y)+(6x-4y)(x+3y)
=-12x²-12xy+3xy-3y²+6x²+18xy-4xy-12y²
=-6x²+5xy-15y²
-6×(-2)²+5×(-2)×1-15×（1）²
=-6×4+5×(-2)×1-15×1
=-24+(-10)-15
=-49

答案

3(-4x+y)(x-y)+2(3x-2y)(x+3y) x=-2 y=1=(-12x+3y)(x-y)+(6x-4y)(x+3y)=-12x²+12xy+3xy-3y²+6x²+18xy-4xy-12y²=-6x²+29xy-15y²当x=-2,y=1时原式=-6x²+29xy-15y²=(-6)*(-2)^...