Question

(1+а/1-а-1-а/1+а):2а/1-а

Answer 1

а≠1 и а≠-1
((1+а)²-(1-а)²)/(1-а²)=(1+а-1+а)(1+а+1-а)/(1-а²)=2а*2/(1-а²)=4а/(1-а²)
4а/(1-а²):2а/(1-а)=4а*(1-а)/(1-а)(1+а)*2а=2/(1+а)