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Math Help - Sketch the graph of the derivative

  1. #1
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    Sketch the graph of the derivative

    1. f(x)=2x^3-3x^2-12x+3
    2. f(x)= (3x^5-20x^3)/(32)

    So I already did most of the problems and think I have a good understanding of how to do this like finding domain, range, concavity, inflection, increasing decreasing, odd and even. But there is one part that I am stuck on. That's finding the x-int and y-int for where the graph intersects. Just wondering if someone can explain to me how to do this. Would I set it = to 0 and solve? I tried that but I get really messy numbers. I also tried factoring by grouping but it doesn't come out right. Please if you can, explain how I would find x and y-intercepts. Thanks!
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  2. #2
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    For finding y-intercepts find f(0), i.e setting all your x equal to zero, and the result will give you the point where the graph intersects the y-axis in the form (0,f(0)).

    For x-intercepts you set f(x)=0, and if it is a function of degree greater than two, and you are not able to use the quadratic formula you could use other methods like sintetic division. But by personal experience most instructors and even books tell you that if the function is to complicated, you are not expected to find the x-ints.
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  3. #3
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    Ahhh I see, thanks! Guess I won't need to find those when I graph it then. I was getting so frustrated at trying to find those!
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  4. #4
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    Quote Originally Posted by nurseme View Post
    Ahhh I see, thanks! Guess I won't need to find those when I graph it then. I was getting so frustrated at trying to find those!
    Exactly, in this point in calculus you are more concern with finding critical points, extrema, concavity, etc. than zeros of the function.
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