400=x2+30x

Solution for 400=x2+30x equation:

400=x2+30x

We move all terms to the left:

400-(x2+30x)=0

We add all the numbers together, and all the variables

-(+x^2+30x)+400=0

We get rid of parentheses

-x^2-30x+400=0

We add all the numbers together, and all the variables

-1x^2-30x+400=0

a = -1; b = -30; c = +400;
Δ = b2-4ac
Δ = -302-4·(-1)·400
Δ = 2500
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2500}=50$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-30)-50}{2*-1}=\frac{-20}{-2}
=+10
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-30)+50}{2*-1}=\frac{80}{-2}
=-40
$