0=-900+450x-25x^2

Solution for 0=-900+450x-25x^2 equation:

0=-900+450x-25x^2

We move all terms to the left:

0-(-900+450x-25x^2)=0

We add all the numbers together, and all the variables

-(-900+450x-25x^2)=0

We get rid of parentheses

25x^2-450x+900=0

a = 25; b = -450; c = +900;
Δ = b2-4ac
Δ = -4502-4·25·900
Δ = 112500
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{112500}=\sqrt{22500*5}=\sqrt{22500}*\sqrt{5}=150\sqrt{5}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-450)-150\sqrt{5}}{2*25}=\frac{450-150\sqrt{5}}{50}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-450)+150\sqrt{5}}{2*25}=\frac{450+150\sqrt{5}}{50}
$