Arturo O. answered 03/24/20
Experienced Physics Teacher for Physics Tutoring
Set it up in the form of a quadratic equation, and then solve it using the quadratic formula. You will get two solutions, so you will need to discriminate which one is correct in the context of the problem.
d = vt + (1/2)at2
(1/2)at2 + vt - d = 0
t = {-v ± √[v2 - 4(a/2)(-d)]} / [2(a/2)]
SImplify, plug in the numbers, evaluate, and finish from here.