8r^2-72r+144=0

Solution for 8r^2-72r+144=0 equation:

8r^2-72r+144=0

a = 8; b = -72; c = +144;
Δ = b2-4ac
Δ = -722-4·8·144
Δ = 576
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{576}=24$
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-72)-24}{2*8}=\frac{48}{16}
=3
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-72)+24}{2*8}=\frac{96}{16}
=6
$