400=60x-2x^2

Solution for 400=60x-2x^2 equation:

400=60x-2x^2

We move all terms to the left:

400-(60x-2x^2)=0

We get rid of parentheses

2x^2-60x+400=0

a = 2; b = -60; c = +400;
Δ = b2-4ac
Δ = -602-4·2·400
Δ = 400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{400}=20$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-60)-20}{2*2}=\frac{40}{4}
=10
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-60)+20}{2*2}=\frac{80}{4}
=20
$