Solve this quadratic equation by completing the square. x2 + 4x = 15

x = -2 + √19, x = -2 - √19

Step-by-step explanation:

Equation: x² + 4x = 15

Complete the square of ax² + bx: x² + 4x + 4

Insert into equation (with balancing): x² + 4x + 4 = 15 + 4

Change form: (x + 2)² = 15 + 4

Combine like terms: (x + 2)² = 19

Square root: x + 2 = ±√19

Isolate x: x = -2 ± √19