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Equation for the tangent line

  1. Jun 19, 2009 #1
    1. The problem statement, all variables and given/known data

    Find the equation for the tangent line to the curve f(x) = 2x3 - 5x - 3 at
    x = 2



    2. Relevant equations
    How do i start this? I'm really confused and have an assignment with a bunch of these questions due tomorrow by midnight... if someone could help me that would be greatly appreciated..



    3. The attempt at a solution
     
  2. jcsd
  3. Jun 20, 2009 #2

    Dick

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    Homework Helper

    The derivative f'(x) will give you the slope of the tangent. x and f(x) will give you a point on the curve. If you have a point and a slope, you have the equation for the tangent line, right?
     
  4. Jun 20, 2009 #3

    HallsofIvy

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    One of the very first things you should learn in Calculus is that the derivative at a point is the slope of the tangent line. And even before Calculus you should have learned how to write the equation of a line given a point and the slope.
     
  5. Jun 20, 2009 #4
    so basically 6x^2-5 ?
     
  6. Jun 20, 2009 #5
    do i then plug in the 2? and solve?
     
  7. Jun 20, 2009 #6

    HallsofIvy

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    "Basically" what about 6x^2- 5?

    Plug 2 into what? Solve what? Please ask complete questions!

    I said before that the derivative at a given value of x is the slope of the tangent line at that x. What is the derivative of your function? What is its value at x= 2?

    Now, how do you find the equation of a line through a given point with given slope? (And what "given point" does this line go through?
     
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