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Unexpected inequality solution from Wolfram Alpha

Posted 16 days ago

There is attached file with my input.
The wolfram gave the x=2 as solution but is supposed to be out of the domain because when x=2 the base of the exponential function equal to 0.

I will be happy for clarification if im wrong

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POSTED BY: Mat Am
7 Replies

You don't need exponential, just elementary powers: 0^2=0*0, 0^3=0*0*0 and so on.

POSTED BY: Gianluca Gorni
Posted 16 days ago

But in fact i do have 2 exponential , and that give me a domain

POSTED BY: Mat Am

Try this:

In[1]:= FunctionDomain[x^y,{x,y}]
Out[1]= (y \[Element] Integers && x != 0) ||
 (y \[Element] Integers && y >= 1) ||
 (x >= 0 && y > 0) ||
 x > 0

When the exponent is a positive integer, there is no restriction at all on the base.

POSTED BY: Gianluca Gorni
Posted 15 days ago

So if i understood comoletly. The base can never be an negative And the base can be 0 if is sure that the exponent is positive?

POSTED BY: Mat Am

The base can be negative if the exponent is integer. For example (-1)^3.

You can do negative numbers raised to a noninteger power if you are comfortable with multivalued complex results. In those cases the usual algebraic rules of powers break down and you must be very careful. I is an endless source of confusion and it turns up regularly on this list.

POSTED BY: Gianluca Gorni

I see no problem with zero raised to a positive integer, like 0^4 or 0^5.

POSTED BY: Gianluca Gorni
Posted 16 days ago

But there isn't domain in exponential function that the base need to be bigger than 0?

POSTED BY: Mat Am
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