A A A 1 A 1      A) A =

Câu 2:

a a a 1 a 1    

 

a) A = : . a 1 a 1              a 1 a ( a - 1) ( a - 1)( a 1) a 1 ( a - 1)   a > 0, a 1    0 a < 1a 1 

b) A < 0

.