420*x^2-2x-4=0

Solution for 420*x^2-2x-4=0 equation:

420x^2-2x-4=0

a = 420; b = -2; c = -4;
Δ = b2-4ac
Δ = -22-4·420·(-4)
Δ = 6724
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{6724}=82$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-2)-82}{2*420}=\frac{-80}{840}
=-2/21
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2)+82}{2*420}=\frac{84}{840}
=1/10
$