Results 1 to 11 of 11

Math Help - Tangents and Normals

  1. #1
    Newbie
    Joined
    Nov 2010
    Posts
    15

    Tangents and Normals

    The curve y=2x^3-6x^2-2x+1 has two tangents, each of which is parallel to the line 2x+y=12. Find their equations??

    Please help!!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,648
    Thanks
    1596
    Awards
    1
    Where is y^\prime = -2~?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Nov 2010
    Posts
    15
    yes based on the straight line equation
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,648
    Thanks
    1596
    Awards
    1
    Quote Originally Posted by Aniff View Post
    yes based on the straight line equation
    WHAT?
    Do you have any idea what this question is about?
    If so, please tell us the basic facts involved.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Nov 2010
    Posts
    15
    sorry me bad I meant that I found y' of the straight line is -2...
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,690
    Thanks
    448
    Quote Originally Posted by Aniff View Post
    sorry me bad I meant that I found y' of the straight line is -2...
    ... which means you need to find the points on the cubic curve where y' = -2
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Newbie
    Joined
    Nov 2010
    Posts
    15
    from what I understood the tangents have the same slope as the straight line so the derivative of the curve y=2x^3-6x^2-2x+1 which is 6x^2-12x-2=-2???
    is that right??
    Follow Math Help Forum on Facebook and Google+

  8. #8
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,690
    Thanks
    448
    Quote Originally Posted by Aniff View Post
    from what I understood the tangents have the same slope as the straight line so the derivative of the curve y=2x^3-6x^2-2x+1 which is 6x^2-12x-2=-2???
    is that right??
    keep going ...
    Follow Math Help Forum on Facebook and Google+

  9. #9
    Newbie
    Joined
    Nov 2010
    Posts
    15
    I'm stuck here...I'm not able to solve the equation...I'm getting weird x values
    Follow Math Help Forum on Facebook and Google+

  10. #10
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,690
    Thanks
    448
    Quote Originally Posted by Aniff View Post
    I'm stuck here...I'm not able to solve the equation...I'm getting weird x values
    6x^2-12x-2=-2

    6x^2 - 12x = 0

    6x(x - 2) = 0

    can you solve it now?
    Follow Math Help Forum on Facebook and Google+

  11. #11
    Newbie
    Joined
    Nov 2010
    Posts
    15
    sure I can...you're rock...thanks a lot
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Tangents and normals
    Posted in the Calculus Forum
    Replies: 1
    Last Post: May 12th 2010, 01:09 AM
  2. tangents and normals
    Posted in the Pre-Calculus Forum
    Replies: 5
    Last Post: June 19th 2009, 05:03 AM
  3. tangents and normals to curve
    Posted in the Calculus Forum
    Replies: 15
    Last Post: September 29th 2008, 03:03 PM
  4. Tangents and Normals
    Posted in the Calculus Forum
    Replies: 12
    Last Post: June 29th 2008, 10:53 AM
  5. Finding Tangents and Normals
    Posted in the Calculus Forum
    Replies: 1
    Last Post: October 16th 2007, 09:46 PM

Search Tags


/mathhelpforum @mathhelpforum