5v^2+15v=90

Solution for 5v^2+15v=90 equation:

5v^2+15v=90

We move all terms to the left:

5v^2+15v-(90)=0

a = 5; b = 15; c = -90;
Δ = b2-4ac
Δ = 152-4·5·(-90)
Δ = 2025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$v_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$v_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2025}=45$
$v_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-45}{2*5}=\frac{-60}{10}
=-6
$
$v_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+45}{2*5}=\frac{30}{10}
=3
$