# How do you solve  9a=-a²-18?

May 29, 2016

$a = - 3$, and $a = - 6$.

#### Explanation:

Start bringing everything on the same side changing the sing when you "jump" the $=$ symbol.

${a}^{2} + 9 a + 18 = 0$

Now you can use the formula for the second order equation

$a = \frac{- 9 \setminus \pm \sqrt{81 - 4 \cdot 18}}{2} = \frac{- 9 \setminus \pm \sqrt{9}}{2} = \frac{- 9 \setminus \pm 3}{2}$.
The solution with the $+$ is
$a = - 3$
and the solution with the $-$ is
$a = - 6$.