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Math Help - Find all the values of x (if any) where the tangent line to the graph of the....

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    Find all the values of x (if any) where the tangent line to the graph of the....

    ....function is horizontal.
    x cubed - 12x + 2

    wouldn't that be 0 and 2. by taking the derivative and solving for x, i get only 2, how do i find the other number(s)?
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  2. #2
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by plstevens View Post
    ....function is horizontal.
    x cubed - 12x + 2

    wouldn't that be 0 and 2. by taking the derivative and solving for x, i get only 2, how do i find the other number(s)?
    The derivative is 3x^2-12

    Setting it equal to zero, we get x^2-4=0\implies x^2=4\implies x={\color{red}\pm}2

    These are the only values where the function has horizontal tangents.

    Does this make sense?

    --Chris
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  3. #3
    Super Member 11rdc11's Avatar
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    Hi to find a horizontal tangent line to a function you take the derivative and equal it to 0

    f(x) = x^3 -12x+2

    f'(x) = 3x^2 -12

    0= 3x^2 -12

    x = 2 and x = -2

    Shoot to late again lol
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    thanks
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  5. #5
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    Find the derivative

    9x^7/5-5x^2+10^4

    Now here i worked this out but the computer keep saying my answer of 63/5x^2/5-10x
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    the computer keep saying its wrong, where did i possibly go wrong on this one
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  7. #7
    Super Member 11rdc11's Avatar
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    9x^{\frac{7}{5}} - 5x^2+10^4

    Is this what it looks like?
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