5x(X+3)=20

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

5x(x+3)=20

We move all terms to the left:

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

We multiply parentheses

5x^2+15x-20=0

a = 5; b = 15; c = -20;
Δ = b2-4ac
Δ = 152-4·5·(-20)
Δ = 625
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{625}=25$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-25}{2*5}=\frac{-40}{10}
=-4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+25}{2*5}=\frac{10}{10}
=1
$