Is there a "proper fraction" command, like in TI-Nspire CAS?

Constantinos shared this question 6 years ago
Answered

Hi to all,


I 'm a graduate teacher and I want to see if I students can use GeoGebra to calculate the derivatives of algebraic expressions.


For example, when I 'm looking for the derivative of f(x)=(x + sqrt(x)) / x²


GeoGebra yields f'(x)=(1 + 1 / 2 / x^(1 / 2)) / x^(2) - (2 * (x + x^(1 / 2)) / x^(3)).


This is very confusing for the students.


How can I make Geogebra yield f'(x)=-1/x^2 - (3/2)x^(-5/2) ?


In other words, how can I make GeoGebra to break the output properly into simple separate fractions (=present the output into a polynomial form)?


In TI-Nspire CAS, there is a command called "proper function" that does this work.

Comments (5)

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1

Hi,


In some cases help:


Simplify[]

Factor[]

or

Expand


Raymond

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1

For example, when I 'm looking for the derivative of f(x)=(x + sqrt(x)) / x²

GeoGebra yields f'(x)=(1 + 1 / 2 / x^(1 / 2)) / x^(2) - (2 * (x + x^(1 / 2)) / x^(3)).

I don't believe, so! In fact, last GG version 4.4.40 performs the shown results: r(x), s(x). While, by algebraically manipulating the given function as per p(x), its derivative q(x) is better simplified.

Cheers

Philippe

https://ggbm.at/5674451a3090abfc40d79f7c4c26fcdf77cf33

Files: 07.png
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Thanks for the replies to everybody


@ Noel:


Yes, PartialFractions doesn't help.


@ Raymond:


I tried them all, nothing useful came out.


@ chaffeur:


I did get the same results q(x) and s(x).

q(x) is more acceptable, but still not expressed as a polynomial with the proper negative exponents notation.

If you try to get the answers using CAS, you will get the weird looking expression I was talking about. See CAS line 3 on my screenshot.

When I deactivated the option "Show rational exponents as roots" in the Advanced Options, I got the result shown in CAS line 1, which is much better than all the other ones.

I tried to simplify that in CAS line 2, but the outcome doesn't look nice.


So the problem is after all that I can't make GeoGebra to properly simplify algebraic expressions containing fractional exponents. As you can see in CAS line 4,

I can't make GeoGebra to yield x^(5/2) for the operation (x^(1/2))*x^2.4fdd86648b34e3967151333f9bfd45f8

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Hi Constantinos,

please, see my photo-comment underneath. Source comes from your previous post.

Cheers

Philippe9a284577f03a8f47cb5bdbd91640c3f3

Files: 09.png
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Thanks Philippe,


I hope too that developers will see this topic and take action! :wink:

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