Answer:
{x = -1 + √13 , x = -1 - √13}
Step-by-step explanation:
Completing the square:
f(x) = x² + 2x - 12
= x² + 2x + 1 - 1 - 12
= (x² + 2x + 1) - 1 - 12
= (x + 1)² - 13
Solving:
f(x) = 0
⇔ (x + 1)² - 13 = 0
⇔ (x + 1)² = 13
⇔ x + 1 = √13 or x + 1 = -√13
⇔ x = -1 + √13 or x = -1 - √13
