先化简,再求值(4x^2-2xy+y^2)(2x+y)-(x^2-y^2)(8x-y),其中x=1,y=-2

题目

先化简,再求值(4x^2-2xy+y^2)(2x+y)-(x^2-y^2)(8x-y),其中x=1,y=-2

答案

原式=8x³+4x²y-4x²y-2xy²+2xy²+y³-8x³+x²y+8xy²-y³
=x²y+8xy²
=-2-32
=-34