3c^2+15c-3=0

Solution for 3c^2+15c-3=0 equation:

3c^2+15c-3=0

a = 3; b = 15; c = -3;
Δ = b2-4ac
Δ = 152-4·3·(-3)
Δ = 261
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{261}=\sqrt{9*29}=\sqrt{9}*\sqrt{29}=3\sqrt{29}$
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-3\sqrt{29}}{2*3}=\frac{-15-3\sqrt{29}}{6}
$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+3\sqrt{29}}{2*3}=\frac{-15+3\sqrt{29}}{6}
$