Results 1 to 7 of 7

Thread: Sketching a curve from a function

  1. #1
    Newbie
    Joined
    Jun 2019
    From
    Kop
    Posts
    5

    Sketching a curve from a function

    Hi all,

    I have a math exam on Tuesday and I am pretty much set when it comes to the exam papers, with one of the exceptions being the style of question shown below:

    A function is defined as y=(x+3)(x+5)(x+8). Sketch this curve on graph paper showing the 3 points where it crosses the X axis (between the x values of -1 and -9).
    Not really sure how to approach this one. I tried getting the points by going in to my calculator and going to table mode and putting the function in to f(x) and then starting at -1 and ending at -9 in steps of 1. This just kept giving 'MATH ERROR'.

    The next part of the questions asks to :

    Find the derivative of y=(x+3)(x+5)(x+8) and plot on the same graph paper as part (a).
    I am unsure how to go about it after getting the derivative of the function, which I calculated to be 3x^2+32x+79. I am unsure how to get the points from this derivative.

    Could someone be so kind to walk me through this question from start to end. Thanks!
    Last edited by deano2727; Aug 23rd 2019 at 05:46 AM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Jun 2013
    From
    Lebanon
    Posts
    1,039
    Thanks
    530

    Re: Sketching a curve from a function

    try starting at $-9$ and ending at $-1$
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member Cervesa's Avatar
    Joined
    Dec 2014
    From
    USA
    Posts
    94
    Thanks
    74

    Re: Sketching a curve from a function

    Not really sure how to approach this one. I tried getting the points by going in to my calculator and going to table mode and putting the function in to f(x) and then starting at -1 and ending at -9 in steps of 1. This just kept giving 'MATH ERROR'.
    works fine in my calculator
    Attached Thumbnails Attached Thumbnails Sketching a curve from a function-table_set.png   Sketching a curve from a function-table_values.png  
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Jun 2019
    From
    Kop
    Posts
    5

    Re: Sketching a curve from a function

    Quote Originally Posted by Idea View Post
    try starting at $-9$ and ending at $-1$
    That worked. Thanks.

    Could someone please demonstrate how to plot the derivative of the used function on to the graph (derivative of function is 3x^2+32x+79).
    Last edited by deano2727; Aug 25th 2019 at 01:47 AM.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Member Cervesa's Avatar
    Joined
    Dec 2014
    From
    USA
    Posts
    94
    Thanks
    74

    Re: Sketching a curve from a function

    $f'(x) = 3x^2+32x+79$

    parabola that opens upward

    zeros at $x = \dfrac{-32 \pm \sqrt{32^2-4(3)(79)}}{6} = \dfrac{-16 \pm \sqrt{19}}{3}$

    parabola vertex at $x = -\dfrac{16}{3}$ and $y = f'\left(-\dfrac{16}{3}\right)$
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor
    Joined
    Jun 2013
    From
    Lebanon
    Posts
    1,039
    Thanks
    530

    Re: Sketching a curve from a function

    Sketching a curve from a function-graphs-f-f-.png
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Newbie
    Joined
    Jun 2019
    From
    Kop
    Posts
    5

    Re: Sketching a curve from a function

    Thanks, guys.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Curve Sketching and Analyzing a Function
    Posted in the Calculus Forum
    Replies: 1
    Last Post: Nov 19th 2017, 01:04 AM
  2. Replies: 2
    Last Post: Mar 13th 2012, 12:35 PM
  3. Curve sketching
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: Jun 9th 2009, 05:01 AM
  4. curve sketching
    Posted in the Calculus Forum
    Replies: 6
    Last Post: Feb 1st 2009, 02:15 PM
  5. Curve sketching
    Posted in the Calculus Forum
    Replies: 2
    Last Post: Mar 24th 2008, 09:48 PM

/mathhelpforum @mathhelpforum