1 2 A A 1 A 1 A (A 1) (A 1) 2 2 2( A 1) 1 2 A ( A 1) ( A 1)=
Câu 2: a) A = a 1 2 a : 1 2 a
a 1 a 1 a (a 1) (a 1)
2
2
2
( a 1) 1 2 a ( a 1) ( a 1)
=
: :
.
a 1 a 1 (a 1)( a 1) a 1 ( a 1)(a 1)
2
( a 1) (a 1)( a 1)
. a 1
.
a 1 ( a 1)
b) a = 2011 - 2 2010 ( 2010 1 )
2