Chapter 9 - Quadratic Functions and Equations - 9-5 Completing the Square - Practice and Problem-Solving Exercises - Page 565: 42

$s=-5,-4$

$s^2+9s+20=0$ or, $s^2+9s=-20$ Compare it with the standard form of quadratic equation $ax^2+bx+c$, we have $a=1, b=9$ To complete the square, add $\dfrac{81}{4}$ on both sides. $s^2+9s+\dfrac{81}{4}=-20+\dfrac{81}{4}$ $\implies (s+\dfrac{9}{2})^2=\dfrac{1}{4}$ $\implies (s+4.5)^2=0.25$ $\implies (s+4.5)=0.5$ and $\implies (s+4.5)=-0.5$ or, $s=-5,-4$