Tìm x biết: a) (2x + 3)(x – 1) + (2x – 3)(1 – x) = 0.

Lời giải:

a) (2x + 3)(x – 1) + (2x – 3)(1 – x) = 0

(2x + 3)(x – 1) – (2x – 3)( x – 1) = 0

(x – 1) (2x + 3 – 2x + 3) = 0

6(x – 1) = 0

x – 1 = 0

x = 1.

Vậy x = 1.

b) (x + 1)(6x² + 2x) + (x – 1)(6x² + 2x) = 0

(6x² + 2x)(x + 1 + x – 1) = 0

2x. 2x(3x + 1) = 0

4x² (3x + 1) = 0

4x² = 0 hoặc 3x + 1 = 0

x = 0 hoặc \({\rm{x}} = \frac{{ - 1}}{3}\).

Vậy x = 0; \({\rm{x}} = \frac{{ - 1}}{3}\).