Using the quadratic formula, we have
x=−b±√b2−4ac2a
From the equation 3x2−4x−5=0, a = 3, b = -4 and c = -5.
∴x=−(−4)±√(−4)2−4(3)(−5)2(3)
= 4±√16+606
= 4±√766
= 4±8.726
= 4+8.726 or 4−8.726
= 12.726 or −4.726
x=2.12 or -0.79