Respuesta :

Answer:

16

Step-by-step explanation:

x² + 8x = 4 ⇔ x² + 8x + 16 = 4 + 16 ⇔ x² + 2×4x + 4² = 20 ⇔ (x + 4)² = (2√5)²

Remark : (2√5)² = 20