題中x-1是在分母上的吧
關(guān)鍵是由x的范圍確定絕對(duì)值內(nèi)的符號(hào),
然后去掉絕對(duì)值號(hào),最后與分母進(jìn)行約分
當(dāng)x>1時(shí),x+1>0,x-1>0 故有
(|x+1||x-1|)/(x-1)=(x+1)(x-1)/(x-1)=x+1
當(dāng)-1≤ x≤1時(shí),x+1≥0,x-1≤0 故有
(|x+1||x-1|)/(x-1)=(x+1)[-(x-1)]/(x-1)=-(x+1)
當(dāng)x<-1時(shí),x+1<0,x-1<0 故有
(|x+1||x-1|)/(x-1)=[-(x+1)][-(x-1)]/(x-1)=x+1