2x(7x-9)=90

Solution for 2x(7x-9)=90 equation:

2x(7x-9)=90

We move all terms to the left:

2x(7x-9)-(90)=0

We multiply parentheses

14x^2-18x-90=0

a = 14; b = -18; c = -90;
Δ = b2-4ac
Δ = -182-4·14·(-90)
Δ = 5364
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:

$\sqrt{\Delta}=\sqrt{5364}=\sqrt{36*149}=\sqrt{36}*\sqrt{149}=6\sqrt{149}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-18)-6\sqrt{149}}{2*14}=\frac{18-6\sqrt{149}}{28}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-18)+6\sqrt{149}}{2*14}=\frac{18+6\sqrt{149}}{28}
$