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

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

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

We add all the numbers together, and all the variables

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

We multiply parentheses ..

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

We get rid of parentheses

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

We add all the numbers together, and all the variables

v^2-14v+45=0

a = 1; b = -14; c = +45;
Δ = b2-4ac
Δ = -142-4·1·45
Δ = 16
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$v_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$v_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{16}=4$
$v_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-14)-4}{2*1}=\frac{10}{2}
=5
$
$v_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-14)+4}{2*1}=\frac{18}{2}
=9
$