## hiralpatel121 3 years ago Can someone please check the attached problems?

1. JakeV8

why yes, I would be happy to :)

2. hiralpatel121

3. imron07

3b), did you just use negative -500 mg for I(t)?

4. JakeV8

yes, it needs to have been 500 = -3t^2 + 126t

5. JakeV8

try quadratic formula again with 0 = -3t^2 + 126t - 500

6. hiralpatel121

I'm lost.

7. JakeV8

http://www.wolframalpha.com/input/?i=500+%3D+-3t^2%2B126t Ibuprofen level starts at zero, take a pill, levels increase past 500, peak, and drop back below 500. The points the quadratic formula produces are the t values that go with the I(t) levels of 500

8. JakeV8

Start your set up by saying I(t) = Ibuprofen level at time t after taking pill. I(t) = -3t^2 + 126t when is I(t) = 500? I(t) = 500 = -3t^2 + 126t 0 = -3t^2 + 126t - 500 then use quadratic formula. Result is 2 t values which are possible times after taking pill before I(t) level of ibuprofen is equal to 500. The problem asks for the longest time, so you would need to select the larger t value.

9. JakeV8

consolation prize... you had part (a) correct :)

10. hiralpatel121

So 3(a) is correct and I have to fix 3(b)?

11. JakeV8

I think prob 4 is right too.

12. JakeV8

ugh bad laptop! Yes, 3b needs fixing, but you were close... just set up I(t) = 500, put in the expression for I(t), subtract 500 from both sides to get -3t^2 +126t - 500 = 0, and then use quadratic formula

13. hiralpatel121

Okay, thank you!

14. JakeV8

you just jumped into it too fast and put the 500 on the wrong side.

15. JakeV8

Always glad to help... I am really really really really really love the fact that you try these problems first and then post them for us to talk through... that is how this site is SUPPOSED to work!!

16. JakeV8

Now I have to get going though :) see you next time :)

17. hiralpatel121

See you next time :) Thank you so much :)