8c+15=-c2

Solution for 8c+15=-c2 equation:

8c+15=-c2

We move all terms to the left:

8c+15-(-c2)=0

We add all the numbers together, and all the variables

-(-1c^2)+8c+15=0

We get rid of parentheses

1c^2+8c+15=0

We add all the numbers together, and all the variables

c^2+8c+15=0

a = 1; b = 8; c = +15;
Δ = b2-4ac
Δ = 82-4·1·15
Δ = 4
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4}=2$
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-2}{2*1}=\frac{-10}{2}
=-5
$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+2}{2*1}=\frac{-6}{2}
=-3
$