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**An object accelerates at the rate of 1.30 m/s^2 over a displacement of 11.8m, reaching a final velocity of 7.00 m/s. For what length of time was it accelerating? Explain the answers.**

**NOTE:**Actually, when I first was about to post this, I finally had gotten the answer I needed. However, I cannot explain why I got these two answers (So now a new question.

**a = 1.30 m/s^2 , d = 11.8m , v = 7 m/s , t = ?**

d = v2t - 1/2at^2

11.8 = 7t - 0.65t^2

0 = 0.65t^2 - 7t + 11.8

d = v2t - 1/2at^2

11.8 = 7t - 0.65t^2

0 = 0.65t^2 - 7t + 11.8

-b [tex]\pm[/tex][tex]\sqrt{b^2-4ac}[/tex]

/2a (The entire equation above)

7 [tex]\pm[/tex][tex]\sqrt{-7^2-4(0.65)(11.8)}[/tex]

/2(0.65) (The entire equation above)

= 7 [tex]\pm[/tex][tex]\sqrt{49-30.68}[/tex]

/1.3 (The entire equation above)

Answer:

(7 + 4.28)/2 = 8.68 s

or

(7 - 4.28)/2 = 2.09 s

Now I know the answer but, I can't explain why there could be two answers. Can anyone explain?