求一数学题的解,整式的运算-完全平方公式,求详解已知x(x-1)-(x方-y)=-2,求(x方+y方)/2-xy的值

Question

求一数学题的解,整式的运算-完全平方公式,求详解
已知 x(x-1)-(x方-y)=-2 ,求(x方+y方)/2 -xy的值

Answer 1

x(x-1)-(x²-y)=-2
x²-x-x²+y=-2
x-y=2
(x²+y²)/2-xy
=½﹙x²-2xy＋y²﹚
=½﹙x－y﹚²
=½×2²
=2