Question

a)  x(2x - 1) - (x - 2)(2x + 3) = 5

b) (x - 3)² - 25 = 0

c) (x - 1) (2 - x) + (x + 3)² = 4 - 2x

Answer 1

a) x(2x - 1) - (x - 2)(2x + 3) = 5

2x² - x - 2x² - 3x + 4x + 6 = 5

0x = -1 (vô lý)

Vậy không tìm được x

b) (x - 3)² - 25 = 0

(x - 3)² - 5² = 0

(x - 3 - 5)(x - 3 + 5) = 0

(x - 8)(x + 2) = 0

\(\Rightarrow\) x - 8 = 0 hoặc x + 2 = 0

*) x - 8 = 0

x = 0 + 8

x = 8

*) x + 2 = 0

x = 0 - 2

x = -2

Vậy x = 8; x = -2

c) (x - 1)(2 - x) + (x + 3)² = 4 - 2x

2x - x² - 2 + x + x² + 6x + 9 = 4 - 2x

9x + 7 = 4 - 2x

9x + 2x = 4 - 7

11x = -3

x = \(\dfrac{-3}{11}\)

Vậy x = \(\dfrac{-3}{11}\)