3x²/(x+1)-(x+1)/x² = 2x取值范围x≠-1且x≠0设t=x²/(x+1),则 (x+1)/x²=1/t原方程即：3t-1/t=23t²-1=2t3t²-2t-1=0(3t+1)(t-1)=0t=1或-1/3即：x²/(x+1)=1或x²/(x+1)=-1/...