(5-u)(5u-9)=0

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

(5-u)(5u-9)=0

We add all the numbers together, and all the variables

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

We multiply parentheses ..

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

We get rid of parentheses

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

We add all the numbers together, and all the variables

-5u^2+34u-45=0

a = -5; b = 34; c = -45;
Δ = b2-4ac
Δ = 342-4·(-5)·(-45)
Δ = 256
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{256}=16$
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(34)-16}{2*-5}=\frac{-50}{-10}
=+5
$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(34)+16}{2*-5}=\frac{-18}{-10}
=1+4/5
$