Помогите плиз 9tg^4x=6tg^2x-1 [-3п/2;0]

Question

Помогите плиз

9tg^4x=6tg^2x-1 [-3п/2;0]

Answer 1

9tg^4x=6tg^2x-1              [-3п/2;0]
9tg^4x - 6tg^2x + 1 = 0 
 tg²x = z
9z² - 6z + 1 = 0
D = 36 - 4*9*1 = 0
z₁ = 6/18
z₁ = 1/3
tg²x = 1/3
1)  tgx = - √3
x = - π/6 + πk, k∈Z
2) tgx = 1/√3
x = π/6 + πn, n∈Z   не принадлежит промежутку  [-3п/2;0]
Ответ: x = - π/6 + πk, k∈Z

Comments

откуда 6/18??