(x²-5x+6)/(x²-4x+3)+(x²-4x+3)/(x²-2x+1)+(x²-3x-4)/(1-x²) ←←你的题目是不是这样的?
=(x-3)(x-2)/(x-1)(x-3)+(x-3)(x-1)/(x-1)²+(x-4)(x+1)/(1-x)(1+x) ←因式分解
=(x-2)/(x-1)+(x-3)/(x-1)+(x+4)/(1-x)
=(x-2)/(x-1)+(x-3)/(x-1)-(x+4)/(x-1)
=(x-1)/(x-1)
=1