13=x(x+2)

Solution for 13=x(x+2) equation:

13=x(x+2)

We move all terms to the left:

13-(x(x+2))=0


We calculate terms in parentheses: -(x(x+2)), so:

x(x+2)

We multiply parentheses

x^2+2x

Back to the equation:

-(x^2+2x)


We get rid of parentheses

-x^2-2x+13=0

We add all the numbers together, and all the variables

-1x^2-2x+13=0

a = -1; b = -2; c = +13;
Δ = b2-4ac
Δ = -22-4·(-1)·13
Δ = 56
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:

$\sqrt{\Delta}=\sqrt{56}=\sqrt{4*14}=\sqrt{4}*\sqrt{14}=2\sqrt{14}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-2)-2\sqrt{14}}{2*-1}=\frac{2-2\sqrt{14}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2)+2\sqrt{14}}{2*-1}=\frac{2+2\sqrt{14}}{-2}
$