Chapter 11 - Section 11.1 - Solving Quadratic Equations by Completing the Square - Vocabulary and Readiness Check - Page 763: 5

9

To solve $x^2+6x=10$ by completing the square, our first step would be to take half of the coefficient of b, square it, and add it to both sides. $(\frac{1}{2}\cdot6)^2=9$ $x^2+6x+9=19$ Therefore, we would have to add 9.