Why is b^(m/n) equal to the mth power of the nth root of b?

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Discussion Overview

The discussion revolves around the expression b^(m/n) and its equivalence to (n√b)^m. Participants explore the underlying principles of exponentiation, particularly in relation to fractional exponents and roots, seeking clarification on why these expressions are considered equal.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions the validity of the expression b^(m/n) = (n√b)^m, expressing confusion about the concept of multiplying a number by itself less than one times.
  • Another participant asserts that b^(m/n) can be interpreted as the nth root of b raised to the mth power, suggesting alternative notations like (n√b)^m.
  • A participant reflects on their earlier misunderstanding and seeks a clearer explanation of the relationship between the two expressions.
  • One participant challenges the equivalence by questioning the definition of exponentiation for non-integer values, particularly in the context of the laws of exponents.
  • Another participant elaborates on the definitions of exponents, explaining how they are extended to include fractional and negative values to maintain consistency in mathematical laws.
  • A later reply acknowledges the clarity of an explanation provided and notes corrections made to earlier posts, although the thread title remains unchanged.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and agreement regarding the equivalence of the expressions. Some participants provide explanations and corrections, while others remain uncertain about the definitions and implications of fractional exponents.

Contextual Notes

There are limitations in the definitions and assumptions regarding exponentiation, particularly concerning fractional and negative exponents. The discussion does not resolve these complexities.

split
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Why does b^(m/n) = (nsqrt(b))^m?

Hi, as the subject says, why does b^(m/n) = (n√b)^m?

I don't understand how you can multiply a number by itself less than one times.

Thanks.

EDIT: Finally GOT IT RIGHT.
 
Last edited:
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b^(m/n)= nã(b^m) "the nth root of b to the m power"
you could also write (nãb)^m
Aaron
 
I meant that but I was just thinking about too many things. It's been fixed. I'm asking for an explanation of why that is true.
 


Originally posted by split
Hi, as the subject says, why does b^(m/n) = (n√m)^m?

I don't know that it does. 31/2=(2[squ]1)1=2?
 
The stupid errors just keep piling up don't they!

I take it you mean: "Why is bm/n= n &radic (b)m?"

Let's start with "I don't understand how you can multiply a number by itself less than one times."

You can't. bn is defined as "multiply b by itself n times" only if n is a positive integer (counting number).

However, in that simple situation, we quickly derive the very useful "laws of exponents": bmbn= bm+n and (bm)n= bnm.

We then define bx for other number so that those laws remain true.

For example, IF the laws of exponents are to be true for x= 0, then we must have bn= bn+0= bnb0. As long as b is not 0 we can divide both sides of the equation by bn to bet b0= 1. That is, we MUST define b0= 1 or the laws of exponents will no longer hold.

Now we can see that bn+(-n)= b0= 1. If the laws of exponents are to hold for negative exponents as well, we must have bnb-n= bn+(-n)= 1 or, again dividing both sides of the equation by bn, b-n= 1/bn.

Finally, if (bm)n= bmn is to be true for all numbers, we must have (b1/m)m= b1= b. Since n &radic (b) is define as "the positive number whose nth power is b, we must define b1/m= m &radic (b).
 
Last edited by a moderator:
Thanks HallsOfIvy, your explanation was very clear.

And yes, the errors kept piling up! I have fixed everything but the subject (I don't believe it can be changed. Am I wrong?) so if anyone wants to read it in the future it should make sense.
 

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