原式=[(x-1)/(x+1) +2x/(x²-1)]÷1/(x²-1)=[(x-1)/(x+1) +2x/(x²-1)]×(x²-1)=(x²-1)×(x-1)/(x+1) +(x²-1)×2x/(x²-1)=(x-1)²+2x=x²-2x+1+2x=x²+1要使代数式有意义，分母不能等于0,x+1≠0 且 x²-1≠0；所以 x≠±1当x=2时原式=2²+1=4+1=5
x²+1
