x2-4x+3分之x2-5x+6+s2-2x+1分之x2-4x+3+1-x2分之x2-3x-4
=(x²-5x+6)/(x²-4x+3)+(x²-4x+3)/(x²-2x+1)-(x²-3x-4)/(1-x²)
=(x-2)(x-3)/(x-1)(x-3)+(x-1)(x-3)/(x-1)²-(x-4)(x+1)/(1+x)(1-x)
=(x-2)/(x-1)+(x-3)/(x-1)+(x-4)/(x-1)
=[x-2+x-3+x-4]/(x-1)
=(3x-9)/(x-1)