21x^2-58x-40=0

Solution for 21x^2-58x-40=0 equation:

21x^2-58x-40=0

a = 21; b = -58; c = -40;
Δ = b2-4ac
Δ = -582-4·21·(-40)
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{-(-58)-82}{2*21}=\frac{-24}{42}
=-4/7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-58)+82}{2*21}=\frac{140}{42}
=3+1/3
$