Why can neither GeoGebra, nor MathWay solve this simple math problem?

Question

$\frac{e^{0.75}}{-0.5^e+10000}$

This doesn't work either:

$\frac{2.72^{0.75}}{-0.5^{2.72}+10000}$

I can even solve it with a calculator.

I don't understand the problem. Did you look up how to correctly enter mathematical expressions in those programs? How did you try to enter them? — Jonas Meyer, Jun 05 '12 at 11:13
http://screencast.com/t/OBW9dbURsXF http://screencast.com/t/Sv3ZzWKJYJMy A = the intersection between a and g. — Friend of Kim, Jun 05 '12 at 11:22

score 4 · Accepted Answer · answered Jun 05 '12 at 11:32

4

First of all, $(-0.5)^e$ is not the same as $-0.5^e$.

Secondly, $x^y$ is not well defined (at least not as a real number) if $x < 0$ and $y$ is not an integer.

answered Jun 05 '12 at 11:32

mrf

I know that there is a difference between (−0.5)^e and −0.5^e, none of them worked. So you are saying that they cannot solve it because of their scripts, not because the math is not supposed to work? – Friend of Kim Jun 05 '12 at 11:39
3

@50ndr33 From your reply in the comment above, you seemed confused about the difference. (You wrote one thing in the question, another in the comment.)
I don't have any of the two programs you mention available, but I know there are some programs that get the priority rules wrong, i.e. interpreting $-0.5^e$ as $(-0.5)^e$. Wolfram Alpha gets it right: http://www.wolframalpha.com/input/?i=e%5E0.75%2F%28-0.5%5Ee%2B10000%29
– mrf Jun 05 '12 at 11:52

score 1 · Answer 2 · answered Jun 05 '12 at 12:26

1

Mathway refuses to numerically evaluate. Geogebra Does evaluate the expression correctly

e^(.75)/(10000-.5^e)

Gives

a=0

but if you right click on a and go to object properties the value says

0.00021

which agrees with google calculator

Why you would want to evaluate this in geogebra is beyond me

answered Jun 05 '12 at 12:26

N8tron

Why you would want to evaluate this in geogebra is beyond me: It was because I wanted to draw this as a graph. But it said undefined with values of 1 or less on the x-axis. (0.5 = x) – Friend of Kim Jun 05 '12 at 13:47
Then as others have stated before me the expression you typed and what you are asking geogebra to evaluate are not the same thing $-.5^e \neq (-.5)^e$. The expression $(-.5)^e$ isn't even well defined. – N8tron Jun 05 '12 at 15:48
So the expression $x^e$ is only a well defined real number if $x \ge 0$. Your calculator may be giving you one of the possible complex multi-valued solutions. – N8tron Jun 05 '12 at 15:49

2 Answers2