(-2x-y)(-2x+y)+(x-3y)²-(2x+y)²-2x(-5y+x),其中x=2,y=-1.它的值是什么?
问题描述:
(-2x-y)(-2x+y)+(x-3y)²-(2x+y)²-2x(-5y+x),其中x=2,y=-1.它的值是什么?
答
(-2x-y)(-2x+y)+(x-3y)²-(2x+y)²-2x(-5y+x)
=4x²-y²+x²-6xy+9y²-4x²-4xy-y²+10xy-2x²
=-x²+7y²
=-2²+7*(-1)²
=-4+7
=3