0=9x^2-54x+72

Solution for 0=9x^2-54x+72 equation:

0=9x^2-54x+72

We move all terms to the left:

0-(9x^2-54x+72)=0

We add all the numbers together, and all the variables

-(9x^2-54x+72)=0

We get rid of parentheses

-9x^2+54x-72=0

a = -9; b = 54; c = -72;
Δ = b2-4ac
Δ = 542-4·(-9)·(-72)
Δ = 324
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{324}=18$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(54)-18}{2*-9}=\frac{-72}{-18}
=+4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(54)+18}{2*-9}=\frac{-36}{-18}
=+2
$