Question

x(x-1)-(x的平方-y)=-2 ,求2分之x的平方+y的平方-xy的值

Answer 1

x(x-1)-(x²-y)=-2

x²-x-x²+y=-2

-x+y=-2

x-y=2

(x²+y²)/2-xy

=(x²-2xy+y²)/2

=(x-y)²/2

=2²/2

=2