How to write a quadratic equation with positive or negative coefficients

How to write a quadratic equation with positive or negative coefficients

oleh Dominique Bauer -
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Since we often use equations in quizzes, I'm opening this discussion in the quiz forum.

Formulas_20200828_0017.png

The question looks like this:



Try it at https://moodleformulas.org/course/view.php?id=36&section=2 ↗

The way I describe above works fine. Does anyone know of an easier way to achieve the same result?

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Re: How to write a quadratic equation with positive or negative coefficients

oleh David Galiana -

Hi Dominique

There is a simpler way to write polynomials using Moodle Formulas: poly() function.

For instance: 

Global variables:

equation=poly("x",[2,-3-5]);

Question text: \\({equation}=0\\) will throw \(2x^2-3x-5=0\)

Sample question attached.
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Re: How to write a quadratic equation with positive or negative coefficients

oleh Ton Boerkoel -
That is very cool, David! I had another work around---that I was proud of---but using the poly() function is brilliant.
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Re: How to write a quadratic equation with positive or negative coefficients

oleh Ton Boerkoel -
There is still the issue when we have polynomial equations with more than one variable x, y z, in which case  poly()  doesn't quite work. Below I have a way (using just builtin functions) to produce nice results. 

For example we would like to write {a11}x+{a12}y+{a13}z nicer.e.g.








Here is the code that produces this


and


Of course you can also code this with Javascript, but, as you can see, it can be done with string operations too.










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Re: How to write a quadratic equation with positive or negative coefficients

oleh Ton Boerkoel -
Here is a slightly improved version. The code maybe easier to read.
 


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Re: How to write a quadratic equation with positive or negative coefficients

oleh Dominique Bauer -
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Hello David,

Of course. What was I thinking!

Thank you for your post.
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