Question

(7x-2)^2-12|7x-2|-28=0

Answer 1

(7x - 2)² - 12|7x - 2| - 28 = 0

заметим |7x - 2|² = (7x - 2)²

|7x - 2|² - 12|7x - 2| - 28 = 0

|7x - 2| = t ≥ 0

t² - 12t - 28 = 0

D = 12² + 4*28 = 144 + 112 = 256 = 16²

t12= (12 +- 16)/2 = -2    14

t1 = -2   нет t ≥ 0

t2 = 14

|7x - 2| = 14

7x - 2 = 14

7x = 16

x = 16/7

7x - 2 = - 14

7x = -12

x = -12/7

ответ 16/7, -12/7