Question

若x(x-1)-(x的平方-y)=-3,则x的平方+y的平方-2xy=?

Answer 1

x(x-1)-(x²-y)=-3

x²-x-x²+y=-3

-x+y=-3

x-y=3

x²+y²-2xy

=(x-y)²

=3²

=9