Question

(1/x-y+1/x+y)÷xy/x^2-y^2

Answer 1

(1/x-y+1/x+y)÷xy/x^2-y^2

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

=(x+y+x-y)/(x^2-y^2)×(x^2-y^2)/xy

=2x/xy

=2/y

2x-6/x-2÷x-3/x^2-4x+4

=2(x-3)/(x-2)×(x-2)^2/(x-3)

=2(x-2)

=2x-4

(1/b-1/a)乘ab/a^2-b^2

=(a-b)/ab×ab/[(a+b)(a-b)]

=1/(a+b)