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Math wiz needed please....money on stars 4 help

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  1. amac1212 amac1212 is offline

    Peoria, IL
    United States

    Posts: 94
    Joined: Sep 06

    Oct 8th, 2008 (10/8/2008 6:17pm)

    Anyone that can help me out please i need to know if i am doing these right....if someone is kind enough i will ship u a little something on stars(it is little but something to say the least) my answers are at the bottom

    1) The amount of radioactive substance remaining after t hours is found with p(t)=4e^-0.002t where

    t is in grams.

    a) How many grams are left after 10 hours?

    b) How fast is the substance decreasing after 10 hours?

    2) The amount of a drug in a person's drugstream is found with M(t)= 12te^-.4t where t is in hours

    and m is in milligrams.

    a) How rapidly is the amount increasing when t=1?

    b) How much drug is in the bloodstream and how rapidly is it changing when t=2.5?

    6) Given x^3+ y^2=9 use implicit differentiation to solve for dy/dx and then find the slope

    of the graph at (2,1).

    I have this but dont know if its right.
    1. a)3.92 b).608g/hour
    2)11.53 mg/hour b) 11.04 mg/sec increasing and 27.6 in the system
    6) I have the deriviative of the fuction which is dy/dx= -3x^2/2y...so whats the slope?
  2. BrOOkLynBaLLeR BrOOkLynBaLLeR is offline

    Pittston, PA
    United States

    Posts: 1,758
    Joined: Jan 07

    Oct 8th, 2008 (10/8/2008 6:23pm) in reply to amac1212

    2-()4*

    ship to kap25
  3. amac1212 amac1212 is offline

    Peoria, IL
    United States

    Posts: 94
    Joined: Sep 06

    Oct 8th, 2008 (10/8/2008 6:25pm) in reply to BrOOkLynBaLLeR

     
    Originally Posted by BrOOkLynBaLLeR View Post

    2-()4*

    ship to kap25

    Double check that i dont what that means...
    Thread Starter
  4. BrOOkLynBaLLeR BrOOkLynBaLLeR is offline

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    Oct 8th, 2008 (10/8/2008 6:27pm) in reply to amac1212

     
    Originally Posted by amac1212 View Post

     
    Originally Posted by BrOOkLynBaLLeR View Post

    2-()4*

    ship to kap25

    Double check that i dont what that means...

    i dont either, but i did stay at a holiday inn last night
  5. BAntares BAntares is offline

    Kansas City, KS
    United States

    Posts: 1,886
    Joined: May 08

    Oct 8th, 2008 (10/8/2008 6:37pm) in reply to BrOOkLynBaLLeR

    i wish i hadn't opened this thread..i feel like an idiot for not remembering how to do this..
  6. WeWaysAwIn WeWaysAwIn is offline

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    Joined: Aug 07

    Oct 8th, 2008 (10/8/2008 6:49pm) in reply to amac1212

     
    Originally Posted by amac1212 View Post

    Anyone that can help me out please i need to know if i am doing these right....if someone is kind enough i will ship u a little something on stars(it is little but something to say the least) my answers are at the bottom

    1) The amount of radioactive substance remaining after t hours is found with p(t)=4e^-0.002t where

    t is in grams.

    a) How many grams are left after 10 hours?

    b) How fast is the substance decreasing after 10 hours?

    2) The amount of a drug in a person's drugstream is found with M(t)= 12te^-.4t where t is in hours

    and m is in milligrams.

    a) How rapidly is the amount increasing when t=1?

    b) How much drug is in the bloodstream and how rapidly is it changing when t=2.5?

    6) Given x^3+ y^2=9 use implicit differentiation to solve for dy/dx and then find the slope

    of the graph at (2,1).

    I have this but dont know if its right.
    1. a)3.92 b).608g/hour
    2)11.53 mg/hour b) 11.04 mg/sec increasing and 27.6 in the system
    6) I have the deriviative of the fuction which is dy/dx= -3x^2/2y...so whats the slope?

    EDIT: good catch on the 2b brianyut

    1
    a is 3.92 right
    b p'(t)=(-.002)(4)e^(-.002t)
    at t=10
    = -.0078 g/hr

    2 chain rule derivative
    (12)(e^-.4t)+(12)(-.4)(t)(e^-.4t)
    t=1
    M'(1)= 4.8263 mg/hr
    b
    t=2.5
    M'(2.5)=0 mg/hr
    M(2.5)=11.0364 mg

    Given x^3+ y^2=9 use implicit differentiation to solve for dy/dx and then find the slope of the graph at (2,1).

    3x2 +2y(dy/dx)=0

    dy/dx = (-3x2)/(2y)

    at (2,1)

    still gives you -6

    This is the way to solve it with implicit differentiation.

    WeWaysAwIn on stars
  7. Rocket Surgeon Rocket Surgeon is offline & brain scientist

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    Oct 8th, 2008 (10/8/2008 6:52pm) in reply to amac1212

    1a) Evaluate p(10) = 4*e^-.002(10) = 3.9207 grams

    1b) Evaluate p'(10) = 4*(-.002)*e^(-.002*10) = -.00784 grams/hour

    2a) Evaluate M'(1) = [12*e^(-.4*1)]+[12*1*(-.4)*e^(-.4*1)] = 4.8263 mg/hr

    2b) Evaluate M(2.5) = 12*2.5*e^(-.4*2.5) = 11.036 mg

    Evaluate M'(2.5) = [12*e^(-.4*2.5)]+[12*2.5*(-.4)*e^(-.4*2.5)] = 0 mg/hr

    6) y = sqrt(9-x^3)

    dy/dx = (1/2)*(9-x^3)^(-1/2)*(-3x^2)

    dydx evaluated at (2,1) = (1/2)*(9-2^3)^(1/2)*(-3*2^2) = -6

    I don't want anything.
  8. Rocket Surgeon Rocket Surgeon is offline & brain scientist

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    Oct 8th, 2008 (10/8/2008 6:53pm) in reply to WeWaysAwIn

     
    Originally Posted by WeWaysAwIn View Post

    2 chain rule derivative
    (12)(e^-.4t)+(12)(-.4)(t)(e^-.4t)
    t=1
    M'(1)= 4.8263 mg/hr
    b
    t=2.5
    M'(2.5)=0 mg/hr
    M(2.5)=4.4146 mg

    Your 2b is wrong.
  9. WeWaysAwIn WeWaysAwIn is offline

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    Joined: Aug 07

    Oct 8th, 2008 (10/8/2008 6:57pm) in reply to Rocket Surgeon

     
    Originally Posted by brianyut View Post

     
    Originally Posted by WeWaysAwIn View Post

    2 chain rule derivative
    (12)(e^-.4t)+(12)(-.4)(t)(e^-.4t)
    t=1
    M'(1)= 4.8263 mg/hr
    b
    t=2.5
    M'(2.5)=0 mg/hr
    M(2.5)=4.4146 mg

    Your 2b is wrong.

    good call I edited the right answer into my post
  10. WeWaysAwIn WeWaysAwIn is offline

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    Oct 8th, 2008 (10/8/2008 7:06pm) in reply to amac1212

    EDIT: yes this is a megaedit. not to make byut look dumb because hes obv a genius and the post that was originally here is misleading but just so there isn't wrong info in the thread.

    Given x^3+ y^2=9 use implicit differentiation to solve for dy/dx and then find the slope of the graph at (2,1).

    3x2 +2y(dy/dx)=0

    dy/dx = (-3x2)/(2y)

    at (2,1)

    still give you -6

    This is the way to solve it with implicit differentiation.
  11. Rocket Surgeon Rocket Surgeon is offline & brain scientist

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    Oct 8th, 2008 (10/8/2008 7:10pm) in reply to WeWaysAwIn

    His wording for that problem is exactly right. That's what implicit differentiation is.

    edit: woah you mega edited. Slow down there editmonster.
  12. Admiral Admiral is offline

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    Oct 8th, 2008 (10/8/2008 7:12pm) in reply to Rocket Surgeon

    I need to find these threads sooner so I can start getting some of the Byut praise. haha
  13. Rocket Surgeon Rocket Surgeon is offline & brain scientist

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    Oct 8th, 2008 (10/8/2008 7:17pm) in reply to Admiral

    You're too busy figuring out compatible materials for a penis implant.
  14. Admiral Admiral is offline

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    Oct 8th, 2008 (10/8/2008 7:20pm) in reply to Rocket Surgeon

    LOL
    touche, tou fucking che
  15. tw1161 tw1161 is offline

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    Oct 8th, 2008 (10/8/2008 7:25pm) in reply to WeWaysAwIn

    i could do it if i had my ti83 with me, im at work, its at home
  16. amac1212 amac1212 is offline

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    Oct 8th, 2008 (10/8/2008 7:28pm) in reply to tw1161

    Brian whats your name on stars? Thanks for the help, i didnt know where to plug in some of those numbers on my calc. so now i see ty again.
    Thread Starter
  17. Rocket Surgeon Rocket Surgeon is offline & brain scientist

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    Oct 8th, 2008 (10/8/2008 7:31pm) in reply to amac1212

     
    Originally Posted by amac1212 View Post

    Brian whats your name on stars? Thanks for the help, i didnt know where to plug in some of those numbers on my calc. so now i see ty again.

    No thanks. I don't need anything, just helpin out.
  18. amac1212 amac1212 is offline

    Peoria, IL
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    Oct 8th, 2008 (10/8/2008 7:48pm) in reply to Rocket Surgeon

    thanks man i appreciate it. Imawina i shipped you a few dollars, thanks for ur help too.
    Thread Starter
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