X(5x+20)=385

Solution for X(5x+20)=385 equation:

X(5X+20)=385

We move all terms to the left:

X(5X+20)-(385)=0

We multiply parentheses

5X^2+20X-385=0

a = 5; b = 20; c = -385;
Δ = b2-4ac
Δ = 202-4·5·(-385)
Δ = 8100
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{8100}=90$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-90}{2*5}=\frac{-110}{10}
=-11
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+90}{2*5}=\frac{70}{10}
=7
$