r^2+9r-1=-15

Solution for r^2+9r-1=-15 equation:

r^2+9r-1=-15

We move all terms to the left:

r^2+9r-1-(-15)=0

We add all the numbers together, and all the variables

r^2+9r+14=0

a = 1; b = 9; c = +14;
Δ = b2-4ac
Δ = 92-4·1·14
Δ = 25
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{25}=5$
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(9)-5}{2*1}=\frac{-14}{2}
=-7
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(9)+5}{2*1}=\frac{-4}{2}
=-2
$