[(x的二次方+的y二次方)-(x-y)的二次方+2y(x-y)]除以4,

问题描述:

[(x的二次方+的y二次方)-(x-y)的二次方+2y(x-y)]除以4,
其中x=负三分之一,y=3

原式=(x²+y²-x²+2xy-y²+2xy-2y²)/4
=(4xy-2y²)/4
=xy-y²/2 把x=-1/3,y=3代入
=-1-9/2
=-11/2