399x^2-4=0

Solution for 399x^2-4=0 equation:

399x^2-4=0

a = 399; b = 0; c = -4;
Δ = b2-4ac
Δ = 02-4·399·(-4)
Δ = 6384
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:

$\sqrt{\Delta}=\sqrt{6384}=\sqrt{16*399}=\sqrt{16}*\sqrt{399}=4\sqrt{399}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-4\sqrt{399}}{2*399}=\frac{0-4\sqrt{399}}{798}
=-\frac{4\sqrt{399}}{798}
=-\frac{2\sqrt{399}}{399}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+4\sqrt{399}}{2*399}=\frac{0+4\sqrt{399}}{798}
=\frac{4\sqrt{399}}{798}
=\frac{2\sqrt{399}}{399}
$