3x(3x-8)=20

Solution for 3x(3x-8)=20 equation:

3x(3x-8)=20

We move all terms to the left:

3x(3x-8)-(20)=0

We multiply parentheses

9x^2-24x-20=0

a = 9; b = -24; c = -20;
Δ = b2-4ac
Δ = -242-4·9·(-20)
Δ = 1296
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1296}=36$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-24)-36}{2*9}=\frac{-12}{18}
=-2/3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-24)+36}{2*9}=\frac{60}{18}
=3+1/3
$