√(x - 1) × √(2x + 6) = x + 3
(x - 1) × (2x + 6) = (x + 3)²
2x² + 6x - 2x - 6 = (x + 3)(x + 3)
2x² + 4x - 6 = x² + 3x + 3x + 9
2x² + 4x - 6 - x² - 6x - 9 = 0
x² - 2x - 15 = 0
D = b² - 4ac
D = 4 - 4 × 1 × ( - 15) = 4 + 60 = √64 = 8
x₁= 2 + 8/ 2 = 5
x₂ = 2 - 8 /2 = - 3
Ответ: x₁ = 5, x₂ = - 3