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Math Help - Help with pattern

  1. #1
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    Help with pattern

    ax^3 + bx^2+cx+d=0 is standard form

    How do I find the a, b, c, and d values given only a data table

    Ex:
    X | Y
    0 | 0
    1 | 3
    2 | 14
    3 | 39
    4 | 84

    What is the equation of that? it's cubic. What's the A B C and D?

    Without using a calculator.

    Thanks in advance
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  2. #2
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by jacob23 View Post
    ax^3 + bx^2+cx+d=0 is standard form

    How do I find the a, b, c, and d values given only a data table

    Ex:
    X | Y
    0 | 0
    1 | 3
    2 | 14
    3 | 39
    4 | 84

    What is the equation of that? it's cubic. What's the A B C and D?

    Without using a calculator.

    Thanks in advance
    y = ax^3 + bx^2+cx+d I suppose?

    Plug the x and y values in.

    So for (0, 0):
    0 = a*0^3 + b*0^2+c*0+d
    means d = 0

    Now plug in the next point and the next point, etc. to get:
    3= a + b + c
    14 = 8a + 4b + 2c
    39 = 27a + 9b + 3c

    Now solve this system of equations.

    -Dan
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  3. #3
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    Thank you, that works and I knew that but that's not what I was looking for I'm looking for something like this

    I want to be able to look at the table and determine the A B C D without having to do an equation. For the Quadratic pattern the A is the last column cut in half, the B is the top of the 1st column after Y minus the A. The C is the Y intercept.

    How do you do I find the A B C D? please explain in detail.

    Thanks again.
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  4. #4
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    Can you figure it out? Please help me out with this.
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