1000000=-5x^2+15000x

Solution for 1000000=-5x^2+15000x equation:

1000000=-5x^2+15000x

We move all terms to the left:

1000000-(-5x^2+15000x)=0

We get rid of parentheses

5x^2-15000x+1000000=0

a = 5; b = -15000; c = +1000000;
Δ = b2-4ac
Δ = -150002-4·5·1000000
Δ = 205000000
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:

$\sqrt{\Delta}=\sqrt{205000000}=\sqrt{1000000*205}=\sqrt{1000000}*\sqrt{205}=1000\sqrt{205}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15000)-1000\sqrt{205}}{2*5}=\frac{15000-1000\sqrt{205}}{10}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15000)+1000\sqrt{205}}{2*5}=\frac{15000+1000\sqrt{205}}{10}
$