Question

若x(x+1)-（x的平方+y）=-3,求2分之x的平方+y的平方-xy的值

Answer 1

x(x+1)-（x²+y）=-3,

x²+x-x²-y=-3

x-y=-3

(x²+y²)/2-xy

=(x²-2xy+y²)/2

=(x-y)²/2

=(-3)²/2

=9/2