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    • Thread Starter

    Find the values of x for which f(x) is an increasing function, given that f(x) equals:
    A) x^4+2x^2
    B) x^4-8x^3

    I understand that you have to differentiate and then solve the equation but I can't get a proper answer

    yes you differentiate then solve

    dy/dx > 0 for increasing

    dy/dx < 0 for decreasing

    As the bear says, solve the inequalities to get answers. Be very careful when you give your final answers, make sure they are the correct inequalities. It may help to sketch the graphs as well.

    (Original post by the bear)
    yes you differentiate then solve

    dy/dx > 0 for increasing

    dy/dx < 0 for decreasing
    Techinially the inequalities should not be strict because the question doesn't ask for where the functions are strictly increasing/decreasing.
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