先化简1/(x+1)-(x+2)/(x^2-1)*(x^2-2x+1)/(x+4x+4),再选一个理想的x的值带入求值

Question

先化简1/(x+1)-(x+2)/(x^2-1)*(x^2-2x+1)/(x+4x+4),再选一个理想的x的值带入求值

Answer 1

原式=1/(x+1)-(x+2)/(x+1)(x-1)*(x-1)²/(x+2)²
=1/(x+1)-1/(x+1)*(x-1)/(x+2)
=(x+2-x+1)/(x+1)(x+2)
=3/(x+1)(x+2)
令x=0
原式=3/1*2
=3/2