3x*6x+9=90

Solution for 3x*6x+9=90 equation:

3x*6x+9=90

We move all terms to the left:

3x*6x+9-(90)=0

We add all the numbers together, and all the variables

3x*6x-81=0

Wy multiply elements

18x^2-81=0

a = 18; b = 0; c = -81;
Δ = b2-4ac
Δ = 02-4·18·(-81)
Δ = 5832
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{5832}=\sqrt{2916*2}=\sqrt{2916}*\sqrt{2}=54\sqrt{2}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-54\sqrt{2}}{2*18}=\frac{0-54\sqrt{2}}{36}
=-\frac{54\sqrt{2}}{36}
=-\frac{3\sqrt{2}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+54\sqrt{2}}{2*18}=\frac{0+54\sqrt{2}}{36}
=\frac{54\sqrt{2}}{36}
=\frac{3\sqrt{2}}{2}
$