3x(2x+5)=20

Solution for 3x(2x+5)=20 equation:

3x(2x+5)=20

We move all terms to the left:

3x(2x+5)-(20)=0

We multiply parentheses

6x^2+15x-20=0

a = 6; b = 15; c = -20;
Δ = b2-4ac
Δ = 152-4·6·(-20)
Δ = 705
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-\sqrt{705}}{2*6}=\frac{-15-\sqrt{705}}{12}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+\sqrt{705}}{2*6}=\frac{-15+\sqrt{705}}{12}
$