SOLVE this using quadratic formula

the formula is:

x=(-b+/- sqrt b^2-4ac)/2a

0=v^2+20v-4800

give me a solution step by step pls

a = 1
b = 20
c = -4800

v = -20 +- sqrt(400 - 4 * 1 * -4800) / 2 * 1

v = -20 +- sqrt(400 + 19,200) / 2

v = -20 +- 140 / 2

v = -160 / 2
v= -80

v = 120 / 2
v = 60