计算[(x²-5x+6)/(x²-4x+3)]+[(x²-4x+3)/(x²-2x+1)]+[(x²-3x-4)/(1-x²)]

问题描述:

计算[(x²-5x+6)/(x²-4x+3)]+[(x²-4x+3)/(x²-2x+1)]+[(x²-3x-4)/(1-x²)]