方程的两边同乘x（x+1），得
x+1=2x，
解得x=1．
检验：把x=1代入x（x+1）=2≠0．
∴原方程的解为：x=1，
故答案为：1
I think that something has to be done to stop the air from being polluted, ______ ?
A．doesn't it
B．don’t I
C．don't they
D．haven't they
