13x^2-4x-20=0

Solution for 13x^2-4x-20=0 equation:

13x^2-4x-20=0

a = 13; b = -4; c = -20;
Δ = b2-4ac
Δ = -42-4·13·(-20)
Δ = 1056
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:

$\sqrt{\Delta}=\sqrt{1056}=\sqrt{16*66}=\sqrt{16}*\sqrt{66}=4\sqrt{66}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-4)-4\sqrt{66}}{2*13}=\frac{4-4\sqrt{66}}{26}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+4\sqrt{66}}{2*13}=\frac{4+4\sqrt{66}}{26}
$