已知xy=2,x-y=3,求(x+y)(x-y)-y^2-(6x^2y-2xy^2)/2y的值.
问题描述:
已知xy=2,x-y=3,求(x+y)(x-y)-y^2-(6x^2y-2xy^2)/2y的值.
答
x-y=3
(x-y)^2=9
x^2-2xy+y^2=9
x^2+y^2=13
(x+y)(x-y)-y^2-(6x^2y-2xy^2)/2y
=x^2-y^2-y^2-3x^2+xy
=-2(x^2+y^2)+xy
=-2*13+2
=-24