已知X+Y=2.求(x方-y方)的平方-8乘(x方+y方)的值?
问题描述:
已知X+Y=2.求(x方-y方)的平方-8乘(x方+y方)的值?
答
已知x+y=2,则:(x²-y²)² -8(x²+y²)=[(x+y)(x-y)]²-8(x²+y²)=4(x-y)²-8(x²+y²)=4(x²-2xy+y²-2x²-2y²)=4(-x²-2xy-y²)=-4(x...