Physics quadratic eq help ASAP! Fast 10 pts!?

Im solving a problem and got stuck, here: Given: V = 25 m/s a = -0.4 m/s^2 Find: t So S=displacement, V=initial velocity, t=time, a=acceleration S = V t + 1/2 a t^2 235 = 25 t + 1/2 (-0.4) t^2 235 = 25 t -0.2 t^2 Solve for t using quadratic equation: t = 10.25 sec So you see, I dont know how to... show more Im solving a problem and got stuck, here:

Given: V = 25 m/s
a = -0.4 m/s^2
Find: t

So S=displacement, V=initial velocity, t=time, a=acceleration

S = V t + 1/2 a t^2
235 = 25 t + 1/2 (-0.4) t^2
235 = 25 t -0.2 t^2

Solve for t using quadratic equation:
t = 10.25 sec

So you see, I dont know how to use quadratic and how it arrived at 10.25 sec. So please show me how with steps, thanks!

Also, if ur interested heres my other questions:
http://answers.yahoo.com/question/index?qid=20131101215247AA7g4Sr
http://answers.yahoo.com/question/index?qid=20131101215823AAYwTqe
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