Question

1、分式化简求值（x平方-8x+16）/(x平方-16),其中x=5；2、x平方-2x/2y-xy,其中x=-1,y=2

Answer 1

1.（x平方-8x+16）/(x平方-16),

=(x-4)(x-4)/[(x+4)(x+4)]

=(x-4)/(x+4)

=(5-4)/(5+4)

=1/9

2、x平方-2x/2y-xy

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

=-x/y

=-(-1/2)

=1/2