Question

初二数学上学期一道化简求值题化简求值（x-y）（x+y）+（x-y）^2-（x-2y）^2,其中x=-1/3,y=3

Answer 1

（x-y）（x+y）+（x-y）^2-（x-2y）^2

=x^2-y^2+x^2-2xy+y^2-(x^2-4xy+4y^2)

=x^2+2xy-4y^2

=(-1/3)^2+2*(-1/3)*3-4*3^2

=1/9-2-36

=-37又8/9