- 3x = √(2 + x - x2)
(- 3x)² = (√2 + x - x²)²
9x² =2 + x - x²
10x² - x - 2 = 0
D = 1 + 80 = 81
X1,2 = (1 + - √81)/ 20
X1 = (1 + 9) / 20 = 1/2 = 0,5
X2 = (1 - 9) / 20 = - 2/5
Проверка:
- 3 * 1/2 = √(2 + 1/2 - (1/2)²) не подходит
- 3*(- 2/5) = √2 - 2/5 - (2/5)²)
6/5 = √(2 - 2/5 - 4/25)
6/5 = √36/25
6/5 = 6/5 - верно Ответ : - 2/5