Question

[(x的二次方+的y二次方)-(x-y)的二次方+2y(x-y)]除以4,

Answer 1

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