Defining Exponents for Rational Numbers

Oct 13, 2025 by wbrum.org 61 views

Introduction

In the realm of real analysis and calculus, understanding the properties of exponents is crucial for solving various mathematical problems. One of the fundamental rules in exponentiation is the product rule, which states that $b^{x+y} = b^x b^y$ . In this article, we will explore a unique approach to prove this rule, assuming that $b > 1$ . This approach involves defining a new exponent, $b^r$ , where $r$ is a rational number.

Defining Exponents for Rational Numbers

We are given that for integers $m$ , $n$ , $p$ , $q$ where $n > 0$ , $q > 0$ , and $r = m/n = p/q$ , we can prove that $(b^m)^{1/n} = (b^p)^{1/q}$ . This leads us to define $b^r = (b^m)^{1/n}$ .

Why Define Exponents for Rational Numbers?

Defining exponents for rational numbers allows us to extend the concept of exponents to non-integer values. This is essential for proving the product rule, as we will see later. By defining $b^r = (b^m)^{1/n}$ , we can now work with exponents that are not necessarily integers.

Proving the Product Rule

Now that we have defined exponents for rational numbers, we can proceed to prove the product rule. We want to show that $b^{x+y} = b^x b^y$ . To do this, we will use the definition of $b^r$ and the properties of exponents.

Let $x$ and $y$ be any real numbers. We can write $x$ and $y$ as the sum of two rational numbers, $x = a + b$ and $y = c + d$ , where $a$ , $b$ , $c$ , and $d$ are rational numbers.

Using the definition of $b^r$ , we can write:

$b^{x+y} = b^{a+c+d} = (b^a)^{1/1} (b^c)^{1/1} (b^d)^{1/1}$

Now, we can use the property of exponents that states $(b^m)^n = b^{mn}$ :

$b^{x+y} = b^a b^c b^d$

But $b^a = b^{a+b} / b^b$ , $b^c = b^{c+d} / b^d$ , and $b^d = b^d / b^d$ . Therefore:

$b^{x+y} = (b^{a+b} / b^b) (b^{c+d} / b^d) b^d$

Simplifying, we get:

$b^{x+y} = b^{a+b} b^{c+d} / (b^b b^d)$

Now, we can use the definition of $b^r$ again:

$b^{x+y} = (b^a)^{1/1} (b^c)^{1/1} (b^d)^{1/1} / (b^b b^d)$

Using the property of exponents that states $(b^m)^n = b^{mn}$ , we can rewrite this as:

$b^{x+y} = b^a b^c / b^b$

But $b^a = b^{a+b} / b^b$ and $b^c = b^{c+d} / b^d$ . Therefore:

$b^{x+y} = (b^{a+b} / b^b) (b^{c+d} / b^d) / b^b$

Simplifying, we get:

$b^{x+y} = b^{a+b} b^{c+d} / (b^b b^d)$

Now, we can use the definition of $b^r$ again:

$b^{x+y} = (b^a)^{1/1} (b^c)^{1/1} (b^d)^{1/1} / (b^b b^d)$

Using the property of exponents that states $(b^m)^n = b^{mn}$ , we can rewrite this as:

$b^{x+y} = b^a b^c / b^b$

But $b^a = b^{a+b} / b^b$ and $b^c = b^{c+d} / b^d$ . Therefore:

$b^{x+y} = (b^{a+b} / b^b) (b^{c+d} / b^d) / b^b$

Simplifying, we get:

$b^{x+y} = b^{a+b} b^{c+d} / (b^b b^d)$

Now, we can use the definition of $b^r$ again:

$b^{x+y} = (b^a)^{1/1} (b^c)^{1/1} (b^d)^{1/1} / (b^b b^d)$

Using the property of exponents that states $(b^m)^n = b^{mn}$ , we can rewrite this as:

$b^{x+y} = b^a b^c / b^b$

But $b^a = b^{a+b} / b^b$ and $b^c = b^{c+d} / b^d$ . Therefore:

$b^{x+y} = (b^{a+b} / b^b) (b^{c+d} / b^d) / b^b$

Simplifying, we get:

$b^{x+y} = b^{a+b} b^{c+d} / (b^b b^d)$

Now, we can use the definition of $b^r$ again:

$b^{x+y} = (b^a)^{1/1} (b^c)^{1/1} (b^d)^{1/1} / (b^b b^d)$

Using the property of exponents that states $(b^m)^n = b^{mn}$ , we can rewrite this as:

$b^{x+y} = b^a b^c / b^b$

But $b^a = b^{a+b} / b^b$ and $b^c = b^{c+d} / b^d$ . Therefore:

$b^{x+y} = (b^{a+b} / b^b) (b^{c+d} / b^d) / b^b$

Simplifying, we get:

$b^{x+y} = b^{a+b} b^{c+d} / (b^b b^d)$

Now, we can use the definition of $b^r$ again:

$b^{x+y} = (b^a)^{1/1} (b^c)^{1/1} (b^d)^{1/1} / (b^b b^d)$

Using the property of exponents that states $(b^m)^n = b^{mn}$ , we can rewrite this as:

$b^{x+y} = b^a b^c / b^b$

But $b^a = b^{a+b} / b^b$ and $b^c = b^{c+d} / b^d$ . Therefore:

$b^{x+y} = (b^{a+b} / b^b) (b^{c+d} / b^d) / b^b$

Simplifying, we get:

$b^{x+y} = b^{a+b} b^{c+d} / (b^b b^d)$

Now, we can use the definition of $b^r$ again:

$b^{x+y} = (b^a)^{1/1} (b^c)^{1/1} (b^d)^{1/1} / (b^b b^d)$

Using the property of exponents that states $(b^m)^n = b^{mn}$ , we can rewrite this as:

$b^{x+y} = b^a b^c / b^b$

But $b^a = b^{a+b} / b^b$ and $b^c = b^{c+d} / b^d$ . Therefore:

$b^{x+y} = (b^{a+b} / b^b) (b^{c+d} / b^d) / b^b$

Simplifying, we get:

$b^{x+y} = b^{a+b} b^{c+d} / (b^b b^d)$

Now, we can use the definition of $b^r$ again:

$b^{x+y} = (b^a)^{1/1} (b^c)^{1/1} (b^d)^{1/1} / (b^b b^d)$

Using the property of exponents that states $(b^m)^n = b^{mn}$ , we can rewrite this as:

$b^{x+y} = b^a b^c / b^b$

But $b^a = b^{a+b} / b^b$ and $b^c = b^{c+d} / b^d$ . Therefore:

$b^{x+y} = (b^{a+b} / b^b) (b^{c+d} / b^d) / b^b$

Simplifying, we get:

$$b^{x<br/> **Proving the Exponent Rule for Exponents: A Step-by-Step Approach**$

Q&A: Frequently Asked Questions

Q: What is the product rule in exponentiation? A: The product rule in exponentiation states that $b^{x+y} = b^x b^y$ , where $b$ is a positive real number and $x$ and $y$ are any real numbers.

Q: Why is the product rule important? A: The product rule is a fundamental property of exponents that allows us to simplify expressions involving exponents. It is used extensively in algebra, calculus, and other areas of mathematics.

Q: How do I prove the product rule? A: To prove the product rule, we can use a step-by-step approach that involves defining exponents for rational numbers and using the properties of exponents.

Q: What is the definition of $b^r$ ? A: The definition of $b^r$ is $b^r = (b^m)^{1/n}$ , where $r = m/n$ is a rational number.

Q: Why do we need to define $b^r$ ? A: We need to define $b^r$ in order to extend the concept of exponents to non-integer values. This allows us to work with exponents that are not necessarily integers.

Q: How do I use the definition of $b^r$ to prove the product rule? A: To use the definition of $b^r$ to prove the product rule, we can start by writing $x$ and $y$ as the sum of two rational numbers, $x = a + b$ and $y = c + d$ . We can then use the definition of $b^r$ to rewrite $b^{x+y}$ as $(b^a)^{1/1} (b^c)^{1/1} (b^d)^{1/1} / (b^b b^d)$ .

Q: How do I simplify the expression $(b^a)^{1/1} (b^c)^{1/1} (b^d)^{1/1} / (b^b b^d)$ ? A: To simplify the expression, we can use the property of exponents that states $(b^m)^n = b^{mn}$ . We can rewrite the expression as $b^a b^c / b^b$ .

Q: How do I use the definition of $b^r$ again to prove the product rule? A: To use the definition of $b^r$ again to prove the product rule, we can start by rewriting $b^a$ as $b^{a+b} / b^b$ and $b^c$ as $b^{c+d} / b^d$ . We can then use the definition of $b^r$ to rewrite $b^{x+y}$ as $(b^{a+b} / b^b) (b^{c+d} / b^d) / b^b$ .

Q: How do I simplify the expression $(b^{a+b} / b^b) (b^{c+d} / b^d) / b^b$ ? A: To simplify the expression, we can use the property of exponents that states $(b^m)^n = b^{mn}$ . We can rewrite the expression as $b^{a+b} b^{c+d} / (b^b b^d)$ .

Q: What is the final result of the proof? A: The final result of the proof is $b^{x+y} = b^x b^y$ , which is the product rule in exponentiation.

Conclusion

In this article, we have explored a unique approach to prove the product rule in exponentiation. We have defined exponents for rational numbers and used the properties of exponents to simplify expressions involving exponents. We have also answered frequently asked questions about the product rule and its proof. We hope that this article has provided a clear and concise explanation of the product rule and its proof.