(x+1分之1+x-1分之1)除以x+1分之x

问题描述:

(x+1分之1+x-1分之1)除以x+1分之x

原式=(x-1+x+1)/(x+1)(x-1)*(x+1)/x
=2x/(x+1)(x-1)*(x+1)/x
=2/(x-1)