21x2-39x-6=0

Solution for 21x2-39x-6=0 equation:

21x^2-39x-6=0

a = 21; b = -39; c = -6;
Δ = b2-4ac
Δ = -392-4·21·(-6)
Δ = 2025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2025}=45$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-39)-45}{2*21}=\frac{-6}{42}
=-1/7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-39)+45}{2*21}=\frac{84}{42}
=2
$