520=2x(x+7)

Solution for 520=2x(x+7) equation:

520=2x(x+7)

We move all terms to the left:

520-(2x(x+7))=0


We calculate terms in parentheses: -(2x(x+7)), so:

2x(x+7)

We multiply parentheses

2x^2+14x

Back to the equation:

-(2x^2+14x)


We get rid of parentheses

-2x^2-14x+520=0

a = -2; b = -14; c = +520;
Δ = b2-4ac
Δ = -142-4·(-2)·520
Δ = 4356
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4356}=66$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-14)-66}{2*-2}=\frac{-52}{-4}
=+13
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-14)+66}{2*-2}=\frac{80}{-4}
=-20
$