Dengan melengkapkan kuadrat sempurna,persamaan x²+4x-21=0 dapat ditulis menjadi...
x² + 4x - 21 = 0
x² + 4x = 21
x² + 4x + 4 = 21 + 4
(x + 2)² = 25
x + 2 = ±√25
x + 2 = ±5
x = ±5 - 2
x₁ = 5 - 2
x₁ = 3
x₂ = -5 - 2
x₂ = -7
[answer.2.content]x² + 4x - 21 = 0
x² + 4x = 21
x² + 4x + 4 = 21 + 4
(x + 2)² = 25
x + 2 = ±√25
x + 2 = ±5
x = ±5 - 2
x₁ = 5 - 2
x₁ = 3
x₂ = -5 - 2
x₂ = -7
[answer.2.content]