Results 1 to 6 of 6

Math Help - Fourth Derivitive Problem ~ (Need Help for Calc Midterm)

  1. #1
    Newbie
    Joined
    Jan 2009
    Posts
    5

    Fourth Derivitive Problem ~ (Need Help for Calc Midterm)

    I've got a question that asks me to take the 4th derivitive of (2x+1)^4 ~ The problem I come across is once it becomes 24(2x+1)^0 I don't understand what the value is...

    I'm not sure if I'm correct on this but (2x+1)^4 differentiated is:
    4(2x+1)^3
    12(2x+1)^2
    24(2x+1)^1
    24(2x+1)^0

    Can anyone tell me if I did something wrong, and then answer my question? >.O
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Oct 2005
    From
    Earth
    Posts
    1,599
    Hey there. You forgot to use the chain rule for all your derivatives so they will all be off.

    d/dx (2x+1)^4 = 4(2x+1)^3 * 2
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Jan 2009
    Posts
    5
    Alright, someone brought the Chain Rule up to me earlier when I asked also

    So, I thought that worked but once I take the first derivitive I became confused because 4(2x+1)^3 *2 when differentiated again for the second derivitive would get rid of the *2 wouldn't it? Or am I completely wrong?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    Joined
    Oct 2005
    From
    Earth
    Posts
    1,599
    Quote Originally Posted by Power Rules View Post
    Alright, someone brought the Chain Rule up to me earlier when I asked also

    So, I thought that worked but once I take the first derivitive I became confused because 4(2x+1)^3 *2 when differentiated again for the second derivitive would get rid of the *2 wouldn't it? Or am I completely wrong?
    Before differentiating again, simplify what you have to make it easier.

    4(2x+1)^3 \times 2 = 8(2x+1)^3

    Now repeat process - \frac{d}{dx} 8(2x+1)^3 = 24(2x+1)^2 \times 2 See the pattern?
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Jan 2009
    Posts
    5
    Alright, that helps a lot. So if I simplify it essentially keeps me from any confusion about what stays and what goes, because the coefficient is all that changes due to the chain rule. Thank you, that really does help.

    If only I'd found this place before the test I had today, I might have done a little better on it. (We're on integration, confusion about the chain rule should have been repaired long ago)
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor
    Joined
    Oct 2005
    From
    Earth
    Posts
    1,599
    Well welcome to the forums and I hope you stick around for all your math help needs
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Calc I Midterm Advice
    Posted in the Calculus Forum
    Replies: 0
    Last Post: February 23rd 2010, 03:25 PM
  2. Calc II midterm review guide
    Posted in the Calculus Forum
    Replies: 1
    Last Post: August 8th 2009, 03:31 PM
  3. Midterm practice problem questions
    Posted in the Calculus Forum
    Replies: 1
    Last Post: November 10th 2008, 05:12 PM
  4. Midterm...Calculus optimization problem
    Posted in the Calculus Forum
    Replies: 1
    Last Post: October 20th 2008, 05:04 AM
  5. Markov's Inequality Problem Help! MIDTERM MONDAY!
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: November 17th 2007, 05:52 PM

Search Tags


/mathhelpforum @mathhelpforum