Question

Tìm x 

a) ( x + 2 )² - ( x - 5 ) ( x + 5 ) = 4

b) x ( x - 4 ) - ( x - 7 )² = 3

c) ( x - 6 ) ( x + 6 ) - ( x + 3 ) ( x - 5 ) = 7

giúp mình nhanh đc ko ạ

Answer 1

a)

$⇔ x^2 + 4x + 4 - x^2 + 25 = 4$
$⇔ 4x + 29 = 4$
$⇔ 4x =  - 25$
$⇔ x = \dfrac{-25}{4}$

b)

$⇔ x^2 - 4x - x^2 + 14x + 49 = 3$
$⇔ 10x = -46$
$⇔ x = \dfrac{-46}{10}$

c)

$⇔ x^2 - 16 - (x^2 - 5x + 3x - 15) = 7$
$⇔ x^2 - 16 - x^2 + 2x + 15 = 7$
$⇔ 2x = 8$
$⇔ x = 4$

Answer 2

a) (x + 2)² - (x - 5)(x + 5) = 4

x² + 4x + 4 - x² + 25 = 4

4x + 29 = 4

4x = 4 - 29

4x = -25

x = -25/4

b) x(x - 4) - (x - 7)² = 3

x² - 4x - x² + 14x - 49 = 3

10x - 49 = 3

10x = 3 + 49

10x = 52

x = 52/10

c) (x - 6)(x + 6) - (x + 3)(x - 5) = 7

x² - 36 - x² + 5x - 3x + 15 = 7

2x - 21 = 7

2x = 7 + 21

2x = 28

x = 28/2

x = 14