√16 + 4x - x² = x + 2
16 + 4x - x² = ( x + 2)²
16 + 4x - x² = ( x + 2)( x + 2)
16 + 4x - x² = x² + 2x + 2x + 4
16 + 4x - x² = x² + 4x + 4
16 + 4x - x² - x² - 4x - 4 = 0
- 2x² + 12 = 0
2x² - 12 = 0
D = b² - 4ac = 0 - 4 × 2 × ( - 12) = 0 + 96 = 96
x₁,₂ = ₊/₋√96 / 4