7x^2-9=18x

Solution for 7x^2-9=18x equation:

7x^2-9=18x

We move all terms to the left:

7x^2-9-(18x)=0

a = 7; b = -18; c = -9;
Δ = b2-4ac
Δ = -182-4·7·(-9)
Δ = 576
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{576}=24$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-18)-24}{2*7}=\frac{-6}{14}
=-3/7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-18)+24}{2*7}=\frac{42}{14}
=3
$