2x(5x+6)=90

Solution for 2x(5x+6)=90 equation:

2x(5x+6)=90

We move all terms to the left:

2x(5x+6)-(90)=0

We multiply parentheses

10x^2+12x-90=0

a = 10; b = 12; c = -90;
Δ = b2-4ac
Δ = 122-4·10·(-90)
Δ = 3744
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:

$\sqrt{\Delta}=\sqrt{3744}=\sqrt{144*26}=\sqrt{144}*\sqrt{26}=12\sqrt{26}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-12\sqrt{26}}{2*10}=\frac{-12-12\sqrt{26}}{20}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+12\sqrt{26}}{2*10}=\frac{-12+12\sqrt{26}}{20}
$