4a^2-60a-40=0

Solution for 4a^2-60a-40=0 equation:

4a^2-60a-40=0

a = 4; b = -60; c = -40;
Δ = b2-4ac
Δ = -602-4·4·(-40)
Δ = 4240
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{4240}=\sqrt{16*265}=\sqrt{16}*\sqrt{265}=4\sqrt{265}$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-60)-4\sqrt{265}}{2*4}=\frac{60-4\sqrt{265}}{8}
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-60)+4\sqrt{265}}{2*4}=\frac{60+4\sqrt{265}}{8}
$