(x-3)/(x-1)-(x-5)/(x-7)=(x^2-8x+7-x^2+2)/(x-1)(x-7)
两边乘(x-1)(x-7)
x^2-10x+21-x^2+6x-5=-5x+9
-4x+16=-5x+9
x=-7
分式方程要检验
经检验x=-7是方程的根