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  1. #1
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    Talking Excel quadratic function calculator

    Hello everyone. I have created a graphic calculator for quadratic function using some advices I saw here on the forum. By this, I want to share this document with the users of the forum.Função Quadratica.xlsm Good luck!

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  3. The Following User Says Thank You to RrR2010 For This Useful Post:

    Maudibe (2014-02-20)

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    Cool, i shall try it...when i eventually need such a thing

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    Thanks. I might use this in class to show how changing the coefficients affects the shape of the parabola.

    While I understand the purpose of the first series of controls (the green for the coefficients and the blue for the graphing window), what do the formulas in the orange boxes do?

    Fred

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    Talking

    The orange boxes is used to show some information about the function, like concavity, function roots, delta value, but they are in portuguese (because it's my native language).

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    thanks.

    for my class, the roots and concavity are useful. We'll skip the delta value.

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    Talking

    xD...

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    5 Star Lounger Maudibe's Avatar
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    Very nicely done!

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    This is very useful to me. But I wish there was an English version.

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    I have difficult with just about any language other than English. However, I do teach algebra and we use most of the features of the spreadsheet - see my posting above about the green and blue controls. A subsequent posting from the author discussed the orange items. Not explicitly mentioned in that post was that the last orange box gives the y-intercept of the parabola.

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    WS Lounge VIP sdckapr's Avatar
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    To clean it up a little (you have the occasional spurious green points at 0,0], I would change your formula in Calculos!E8 to:
    Code:
    =IF(delta<0,NA(),IF(coef_a=0,-coef_c/coef_b,(-coef_b+SQRT(delta))/(2*coef_a)))
    and in Calculos!F8 to:
    Code:
    =IF(delta<0,NA(),IF(coef_a=0,-coef_c/coef_b,(-coef_b-SQRT(delta))/(2*coef_a)))
    I also would recommend including the Y-Intercept when you have a line (that is a non-quadratic when coef_a = 0). Instead of displaying "a=?", display the line's Y-Intercept would be more. In Função!C19:

    Code:
    =IF(coef_a=0,"a= [" & round(Calculos!E8,2) & "; 0]",IF(delta<0,"Essa equação não possui raízes reais",IF(delta=0,"A raíz dessa equação é "& ROUND(Calculos!E8,2),"As raízes dessa equação são ["& ROUND(Calculos!E8,2)& "; 0] e ["& ROUND(Calculos!F8,2)& "; 0]")))
    Steve

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    Oh, thanks for that. I'll change this and re-post. And I'll try to do an english version too. Cya...

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    WS Lounge VIP sdckapr's Avatar
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    In case you were not aware, in English, what you term "Delta" is called the "discriminant" [the symbol for it is the uppercase Greek Delta (Δ)].

    A style point, you probably should either refer to the intersection points for the parabola and the X-Axis (for example, [5.3; 0] and [6.2; 0]) or the roots of the quadratic (for example, 5.3 and 6.2). The roots are not points they are just the X-values that solve the equation 0= Ax² + Bx + C. [though graphically they represent the intersection of the curve Y= Ax² + Bx + C and the X-Axis]. You conflate the concepts in several calculations.

    Steve
    Last edited by sdckapr; 2014-02-21 at 13:47.

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    Hey Steve, I'll be glad if you make a better version (or fix my version of that haha). If you can, make it and post for us
    It'll be good for me to learn more about this topic and about excel...thx

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    WS Lounge VIP sdckapr's Avatar
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    I can help anyone who wants to improve it. I have no need for it, so don't know what features would be desired to improve it. My comments were to correct what I considered errors and to help with some of the mathematical terms in English.

    Steve

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    For high school students, it would be useful to use the discriminant to tell the types of roots.

    b^2-4ac = 0 : 1 real root
    b^2-4ac < 0 : no real roots
    b^2-4ac > 0 : 2 real roots

    Might also indicate that if the coefficient of x^2 is positive, the parabola will open upward; otherwise opens downward.

    Just two thoughts that came to my mind.

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