Giải các bất phương trình: a) 3(2x – 3)(2x + 3) > 12x2 + 2x; b) (2x + 1)(5x – 3) > 10x2 + 2x + 1.

a) 3(2x – 3)(2x + 3) > 12x² + 2x

3(4x² – 9) > 12x² + 2x

12x² – 27 > 12x² + 2x

–27 > 2x

2x < –27

x<−272.

Vậy x<−272.

b) (2x + 1)(5x – 3) > 10x² + 2x + 1.

10x² – x – 3 > 10x² + 2x + 1.

–x – 3 > 2x + 1

–x – 2x > 1 + 3

–3x > 4

x<4−3

x<−43.

Vậy x<−43.