(2-x)(5-x)=(x-2)(x-5)
所以最简公分母是(x-1)(x-2)(x-3)(x-5)
所以
3/(x-1)(x-2)=3(x-3)(x-5)/(x-1)(x-2)(x-3)(x-5)
4/(2-x)(5-x)=4(x-1)(x-3)/(x-1)(x-2)(x-3)(x-5)
5/(x-3)=5(x-1)(x-2)(x-5)/(x-1)(x-2)(x-3)(x-5)