Question

Bài 3: Giải các phương trình sau

a. (3x + 2)² – (3x – 2)² = 5x + 38

b. 3(x – 2)² + 9(x – 1) = 3(^x2 + x – 3)

c. (x + 3)² – (x - 3)² = 6x + 8

d. (x – 1)³ – x(x + 1)² = 5x (2 – x) – 11(x + 2)

e. (x + 1)(x² – x + 1) – 2x = x(x – 1)(x + 1)

Answer 1

a) (3x + 2)² - (3x - 2)² = 5x + 38

<=> 6x.4 = 5x + 38 <=> 19x = 38 <=> x = 2

b) 3(x - 2)² + 9(x - 1) = 3(x² + x - 3)

<=> 3x² - 12x + 12 + 9x - 9 = 3x² + 3x - 9

<=> -6x = -12 <=> x = 2

c) (x + 3)² - (x - 3)² = 6x + 8

<=> 2x.6 = 6x + 8 <=> 6x = 8 <=> x = 4/3

d) (x - 1)³ - x(x + 1)² = 5x(2 - x) - 11(x + 2)

<=> x³ - 3x² + 3x - 1 - x³ - 2x² - x = 10x - 5x² - 11x - 22

<=> 3x = -21 <=> x = -7

e) (x + 1)(x² - x + 1) - 2x = x(x - 1)(x + 1)

<=> x³ - 1 - 2x = x³ - x

<=> x = -1