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Math Help - Finding equation of a cubic function?

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    Finding equation of a cubic function?

    How do you do find the equation of a cubic function?
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  2. #2
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    Quote Originally Posted by llamajuice View Post
    How do you do find the equation of a cubic function?
    find what ... zeros?

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    theres no zeroes.
    like its just a normal graph and i need to find an equation that models the behavior of the graph.
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    Quote Originally Posted by llamajuice View Post
    theres no zeroes.
    like its just a normal graph and i need to find an equation that models the behavior of the graph.
    ... how do you know the data models a cubic equation?
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    because it looks like one.
    well first i just plotted the points into excel then i tried all the lines of best fit to see which one it matched. It could also be a sine graph thing, but any polynomial of a degree of 3 or higher works too so i thought finding a cubic function that matches it would be easiest.
    do i just sub in points into y=ax^3 +bx^2 +cx +d to get 4 formulas then solve?
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    Quote Originally Posted by llamajuice View Post
    because it looks like one.
    well first i just plotted the points into excel then i tried all the lines of best fit to see which one it matched. It could also be a sine graph thing, but any polynomial of a degree of 3 or higher works too so i thought finding a cubic function that matches it would be easiest.
    do i just sub in points into y=ax^3 +bx^2 +cx +d to get 4 formulas then solve?
    give it a go ... I cannot make a judgement w/o knowing how the data originated.
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    its like height vs age so theres no x- intercepts
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    Quote Originally Posted by llamajuice View Post
    its like height vs age so theres no x- intercepts
    Height vs age is likely to be linear since there's a direct correlation. Best thing to do is plot in excel and guess the best fit
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    scratch that its body mass index
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