20x+3x^2=135

Solution for 20x+3x^2=135 equation:

20x+3x^2=135

We move all terms to the left:

20x+3x^2-(135)=0

a = 3; b = 20; c = -135;
Δ = b2-4ac
Δ = 202-4·3·(-135)
Δ = 2020
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:

$\sqrt{\Delta}=\sqrt{2020}=\sqrt{4*505}=\sqrt{4}*\sqrt{505}=2\sqrt{505}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-2\sqrt{505}}{2*3}=\frac{-20-2\sqrt{505}}{6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+2\sqrt{505}}{2*3}=\frac{-20+2\sqrt{505}}{6}
$