Results 1 to 4 of 4

Math Help - equation of a tangent question

  1. #1
    Junior Member
    Joined
    Oct 2009
    Posts
    68

    equation of a tangent question

    Consider the function f(x)=3x^2-5x+k. The equation of the tangent to the graph of f(x) at x=p is y=7x-9. Find p and k.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member Dinkydoe's Avatar
    Joined
    Dec 2009
    Posts
    411
    Observe that f'(p) = y'(p) \Leftrightarrow 6p-5 = 7

    Solve for p and use the fact that f(p)= 3p^2-5p+k = 7p-9 to solve for k
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    Nov 2009
    Posts
    202
    u must know the following before solving this problem:
    1)tangent is nothing but the gradient ie dy/dx=f'(x).
    2)for a line y=mx+c the gradient is given by m.
    3)the answers are p=2 and k=12.are they correct???
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member
    Joined
    Nov 2009
    Posts
    202
    u must know the following before solving this problem:
    1)tangent is nothing but the gradient ie dy/dx=f'(x).
    2)for a line y=mx+c the gradient is given by m.
    3)the answers are p=2 and k=12.are they correct???
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 6
    Last Post: January 12th 2011, 02:38 PM
  2. equation of tangent question
    Posted in the Calculus Forum
    Replies: 2
    Last Post: October 12th 2009, 05:22 AM
  3. equation of tangent #1
    Posted in the Calculus Forum
    Replies: 7
    Last Post: August 6th 2009, 11:51 AM
  4. equation of tangent #2
    Posted in the Calculus Forum
    Replies: 3
    Last Post: August 5th 2009, 01:13 PM
  5. Equation Of A Tangent Q
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: October 6th 2008, 08:32 PM

Search Tags


/mathhelpforum @mathhelpforum