The safe stopping distance d, in metres, of a motorcycle on grasss is given by the function?

Question

d=0.02(3v*v + 20v + 1000) where v=m/s
determine the speed at which the safe stopping distance is 30m, correct to one decimal.

Answer 1

You have a quadratic:
3*0.02*v^2 +20*0.02*v +1000*0.02-d = 0
Solve it and take the positive root.