4x^2-36x+81=9

Solution for 4x^2-36x+81=9 equation:

4x^2-36x+81=9

We move all terms to the left:

4x^2-36x+81-(9)=0

We add all the numbers together, and all the variables

4x^2-36x+72=0

a = 4; b = -36; c = +72;
Δ = b2-4ac
Δ = -362-4·4·72
Δ = 144
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{144}=12$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-36)-12}{2*4}=\frac{24}{8}
=3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-36)+12}{2*4}=\frac{48}{8}
=6
$