2x(x+4)=26

Solution for 2x(x+4)=26 equation:

2x(x+4)=26

We move all terms to the left:

2x(x+4)-(26)=0

We multiply parentheses

2x^2+8x-26=0

a = 2; b = 8; c = -26;
Δ = b2-4ac
Δ = 82-4·2·(-26)
Δ = 272
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:

$\sqrt{\Delta}=\sqrt{272}=\sqrt{16*17}=\sqrt{16}*\sqrt{17}=4\sqrt{17}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-4\sqrt{17}}{2*2}=\frac{-8-4\sqrt{17}}{4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+4\sqrt{17}}{2*2}=\frac{-8+4\sqrt{17}}{4}
$