Chapter 8 - Section 8.2 - The Quadratic Formula - Exercise Set - Page 607: 2

{$-3,-5$}

Quadratic formula suggests that $x=\dfrac{-b \pm \sqrt{b^2-4ac}}{2a}$ Given: $x^2+8x+15=0$ Thus, $x=\dfrac{-8 \pm \sqrt{(8)^2-4(1)(15)}}{2(1)}$ or, $x=\dfrac{-8 \pm 2}{2}$ or, $x=\dfrac{-8 + 2}{2}=-3$ and $x=\dfrac{-8 -2}{2}=-5$ Our solution set is: {$-3,-5$}