①x/(x2-1) ·(x2+x)/x2其中x=2 ②(x2-1)/(x2+4x+4)÷(x+1).(x+2﹚/﹙1-x﹚其中x=-3
问题描述:
①x/(x2-1) ·(x2+x)/x2其中x=2 ②(x2-1)/(x2+4x+4)÷(x+1).(x+2﹚/﹙1-x﹚其中x=-3
答
①x/(x^2-1) ·(x^2+x)/x^2=x^2(x+1)/[(x+1)(x-1)x^2]=1/(x-1)=1②(x^2-1)/(x^2+4x+4)÷(x+1).(x+2﹚/﹙1-x﹚=-(x-1)(x+1)(x-1)/[(x+2)^2(x+1).(x+2﹚]=-(x-1)²/(x+2)³=-16/(-1)=16