Chapter 8 - Sections 8.1-8.3 - Integrated Review - Summary on Solving Quadratic Equations - Page 504: 5

$x=-1\pm\sqrt{13}$

Using the completing the square method, the solutions of the given quadratic equation, $ x^2+2x-12=0 ,$ is \begin{array}{l}\require{cancel} x^2+2x=12 \\\\ x^2+2x+\left( \dfrac{2}{2}\right)^2=12+\left( \dfrac{2}{2}\right)^2 \\\\ x^2+2x+1=12+1 \\\\ (x+1)^2=13 \\\\ x+1=\pm\sqrt{13} \\\\ x=-1\pm\sqrt{13} .\end{array}