(5-v)(5v+9)=0

Solution for (5-v)(5v+9)=0 equation:

(5-v)(5v+9)=0

We add all the numbers together, and all the variables

(-1v+5)(5v+9)=0

We multiply parentheses ..

(-5v^2-9v+25v+45)=0

We get rid of parentheses

-5v^2-9v+25v+45=0

We add all the numbers together, and all the variables

-5v^2+16v+45=0

a = -5; b = 16; c = +45;
Δ = b2-4ac
Δ = 162-4·(-5)·45
Δ = 1156
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$v_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$v_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1156}=34$
$v_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(16)-34}{2*-5}=\frac{-50}{-10}
=+5
$
$v_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(16)+34}{2*-5}=\frac{18}{-10}
=-1+4/5
$