x+1/x-1-4/x2-1=-1x-1-1+1+1/x-4/x2=0x-1+1/x-4/x2=0x³-x²+x-4=0有一个实数解：x=1.74295920216631......
（x+1）/（x-1）-4/（x2-1）=-1(x+1)^2-4=1-x^2(x+1+2)(x+1-2)=1-x^2(x+3)(x-1)=1-x^2x+3=-(x+1)2x=-4x=-2
