(6+x)x=280

Solution for (6+x)x=280 equation:

(6+x)x=280

We move all terms to the left:

(6+x)x-(280)=0

We add all the numbers together, and all the variables

(x+6)x-280=0

We multiply parentheses

x^2+6x-280=0

a = 1; b = 6; c = -280;
Δ = b2-4ac
Δ = 62-4·1·(-280)
Δ = 1156
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1156}=34$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-34}{2*1}=\frac{-40}{2}
=-20
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+34}{2*1}=\frac{28}{2}
=14
$