求做一道数学题先化简分式（x-1分之3x减x+1分之x）除x2次方减一分之x减1再取一个和适的值代入求值

Question

求做一道数学题
先化简分式（x-1分之3x减x+1分之x）除x2次方减一分之x减1再取一个和适的值代入求值

Answer 1

（x-1分之3x减x+1分之x）除x2次方减一分之x减1
=[3x/(x-1)-x/(x+1)]/[(x-1)/(x²-1)]?
=[3x(x+1)/(x²-1)-x(x-1)/(x²-1)]/[(x-1)/(x²-1)]
=[(3x²+3x-x²+x)/(x²-1)]/[(x-1)/(x²-1)]
=2(x²+2x)/(x-1)
若x=2,
原式=2(2²+2*2)/(2-1)=16/(1)=16;