Question

Tìm x :

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

b) (x + 2)(x -2) - (x + 1)² = 7

c) 6x² - (2x + 1)(3x - 2) = 1

d) (x + 2)(x + 3) - (x - 2)(x + 1) = 2

e) 6(x - 1)( x + 1) - (2x - 1)(3x + 2) + 3 = 0

Answer 1

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

x + 2 - x(x + 3) - 2 = 0

x + x(x + 3) = 0

x(1 + x + 3) = 0

x(x + 4) = 0

x = 0 hoặc x + 4 = 0

*) x + 4 = 0

x = -4

Vậy x = -4; x = 0

b) (x + 2)(x - 2) - (x + 1)² = 7

x² - 4 - x² - 2x - 1 = 7

-2x - 5 = 7

-2x = 7 + 5

-2x = 12

x = 12 : (-2)

x = -6

c) 6x² - (2x + 1)(3x - 2) = 1

6x² - 6x² + 4x - 3x + 2 = 1

x + 2 = 1

x = 1 - 2

x = -1

d) (x + 2)(x + 3) - (x - 2)(x + 1) = 2

x² + 3x + 2x + 6 - x² - x + 2x + 2 = 2

6x + 8 = 2

6x = 2 - 8

6x = -6

x = -6 : 6

x = -1

e) 6(x - 1)(x + 1) - (2x - 1)(3x + 2) + 3 = 0

6x² - 6 - 6x² - 4x + 3x + 2 + 3 = 0

-x - 1 = 0

x = -1