r^2+8r=153

Solution for r^2+8r=153 equation:

r^2+8r=153

We move all terms to the left:

r^2+8r-(153)=0

a = 1; b = 8; c = -153;
Δ = b2-4ac
Δ = 82-4·1·(-153)
Δ = 676
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{676}=26$
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-26}{2*1}=\frac{-34}{2}
=-17
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+26}{2*1}=\frac{18}{2}
=9
$