Question

先化简,在求值.[(xy+2)(xy-2)-2(x^2y^2-2)]/xy,其中x=10,y=-1/25

Answer 1

[(xy+2)(xy-2)-2(x^2y^2-2)]/xy

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

=(-x^2y^2)/xy

=-xy

因为：x=10,y=-1/25

所以：-xy=-10*-1/25

=2/5