2(x2+4x)+14=399

Solution for 2(x2+4x)+14=399 equation:

2(x2+4x)+14=399

We move all terms to the left:

2(x2+4x)+14-(399)=0

We add all the numbers together, and all the variables

2(+x^2+4x)+14-399=0

We add all the numbers together, and all the variables

2(+x^2+4x)-385=0

We multiply parentheses

2x^2+8x-385=0

a = 2; b = 8; c = -385;
Δ = b2-4ac
Δ = 82-4·2·(-385)
Δ = 3144
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:

$\sqrt{\Delta}=\sqrt{3144}=\sqrt{4*786}=\sqrt{4}*\sqrt{786}=2\sqrt{786}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-2\sqrt{786}}{2*2}=\frac{-8-2\sqrt{786}}{4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+2\sqrt{786}}{2*2}=\frac{-8+2\sqrt{786}}{4}
$