通分:a/(a-b)( b-c),b/(b-a) (c-b)

问题描述:

通分:a/(a-b)( b-c),b/(b-a) (c-b)

∵(b-a) =-(a-b)
(c-b)=-(b-c)
∴负负得正,即b/(b-a) (c-b)=b/(a-b) (b-c)