(х + 5) * (х - 3) = 0
х² - 3х + 5х - 15 = 0
х² + 2х - 15 = 0
D = 2² - 4 * 1 * (-15) = 4 + 60 = 64
- 2 - √64 - 2 - 8
х₁ = ----------------- = ---------- = - 10/2 = - 5
2 * 1 2
- 2 + √64 8 - 2
х₂ = ---------------- = ----------- = 6/2 = 3
2 * 1 2
Ответ: х₁ = - 5 и х₂ = 3