Completing the square

How do you solve the equation by completing the square?
x² + 4x = 10

---

x² + 4x = 10
x² + 4x + 4 = 10 + 4  {took half of the b term, squared it, and added to both sides}
x² + 4x + 4 = 14  {combined like terms}
(x + 2)² = 14  {factored the left side in to squared form}
x + 2 = ±√14  {took the square root of each side}
x = -2 ± √14  {subtracted 2 from each side}

{When I say "half of the b term", I mean half of 4, the coefficient of x.  This would be 2, and if you square it and add it to both sides, you are adding 4 to each side.}

Now get to work, you have squares to complete!

Ask Algebra House