1. Tính

a. (2a2 + b2)2

b. (x2 - 0.1)2

c. (a2 + 5) .( 5 - a2)

2. Rút gọn

(4.x +1)2 + (2x - 1)2 - 8 (x - 1) (x +1)

3. Tìm x

(3x -1)2 + 2 ( x +3) 2 + 11 (x +1) ( 1 - x) = 6