(1)-15x/20x^2
问题描述：
(1)-15x/20x^2
(2)-2ac^2/-14a^2bc
(3)x-y/(y-x)^3
(4)x^2-9/6-2x
(5)a^2+2ab+b^2/a^2-b^2
(6)x^2-1/x-x^2
答
(1)-3/4x
(2)c/7ab
(3)-1/(x-y)^2
(4)-(x+3)/2
(5)(a+b)/(a-b)
(6)-(x+1)/x