300=3x+(x*x)

Solution for 300=3x+(x*x) equation:

300=3x+(x*x)

We move all terms to the left:

300-(3x+(x*x))=0

We add all the numbers together, and all the variables

-(3x+(+x*x))+300=0


We calculate terms in parentheses: -(3x+(+x*x)), so:

3x+(+x*x)

We get rid of parentheses

3x+x*x

Wy multiply elements

x^2+3x

Back to the equation:

-(x^2+3x)


We get rid of parentheses

-x^2-3x+300=0

We add all the numbers together, and all the variables

-1x^2-3x+300=0

a = -1; b = -3; c = +300;
Δ = b2-4ac
Δ = -32-4·(-1)·300
Δ = 1209
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-3)-\sqrt{1209}}{2*-1}=\frac{3-\sqrt{1209}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3)+\sqrt{1209}}{2*-1}=\frac{3+\sqrt{1209}}{-2}
$