Question 49409
Solve by completing the square:

{{{x^2+2x-15 = 0}}} First, add 15 to both sides of the equation.
{{{x^2+2x = 15}}}
Since the coefficient of the {{{x^2}}} term is 1, you can complete the square by adding the square of half the coefficient of the x-term, which is: {{{(2/2)^2 = 1}}}, to both sides of the equation.
{{{x^2+2x+1 = 16}}} Now factor the left sides of the equation.
{{{(x+1)^2 = 16}}} Next, take the square root of both sides.
{{{x+1 = sqrt(16)}}} and {{{x+1 = -sqrt(16)}}} Finally, solve for x.
{{{x = -1+sqrt(16)}}}  {{{x = -1+4}}} {{{x = 3}}}
{{{x = -1-sqrt(16)}}}  {{{x = -1-4}}} {{{x = -5}}}