Question

giải phương trình:

(3x+1)²-(3x-1)(3x+1)=1

36x²-25-x(6x-5)=0

Answer 1

(3x + 1)² - (3x - 1).(3x + 1) = 1

<=> (3x + 1).[(3x + 1) - (3x - 1)] = 1

<=> (3x + 1).(3x + 1 - 3x + 1) = 1

<=> (3x + 1).2 = 1

<=> 3x + 1 = 1/2

<=> 3x = -1/2

<=> x = -1/6

Vậy S = {-1/6}.

36x² - 25 - x.(6x - 5) = 0

<=> (36x² - 25) - x.(6x - 5) = 0

<=> [(6x)² - 5²] - x.(6x - 5) = 0

<=> (6x - 5).(6x + 5) - x.(6x - 5) = 0

<=> (6x - 5).(6x + 5 - x) = 0

<=> (6x - 5).(5x + 5) = 0

<=> 5.(6x - 5).(x + 1) = 0

<=> 6x - 5 = 0 hoặc x + 1 = 0

<=> x = 5/6 hoặc x = -1

Vậy S = {-1; 5/6}.