Question

What number should be added to both sides to complete the square? x^2 + 8x = 4

16
8
4
32

Answer 1

16

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