(2n+1)(2n+3)(2n+5)...(4n-1) Is Equal To

4 min read Jun 16, 2024
(2n+1)(2n+3)(2n+5)...(4n-1) Is Equal To

Proving the Equality of (2n+1)(2n+3)(2n+5)...(4n-1)

This article explores the fascinating mathematical expression (2n+1)(2n+3)(2n+5)...(4n-1) and demonstrates its equality to a more concise form. We will utilize mathematical induction to prove this intriguing relationship.

Understanding the Expression

The expression (2n+1)(2n+3)(2n+5)...(4n-1) represents the product of consecutive odd numbers starting from (2n+1) and ending at (4n-1). For example, if n = 2, the expression becomes (22 + 1)(22 + 3)(2*2 + 5) = 5 * 7 * 9.

Proof by Induction

Base Case: Let's begin with the base case where n = 1. The expression becomes (2*1 + 1) = 3, which is indeed equal to itself.

Inductive Hypothesis: Assume that the expression holds true for some arbitrary integer k. This means that:

(2k + 1)(2k + 3)(2k + 5)...(4k - 1) = a function of k

Inductive Step: We need to prove that the expression also holds true for k+1. This means we need to show that:

(2(k+1) + 1)(2(k+1) + 3)(2(k+1) + 5)...(4(k+1) - 1) = a function of (k+1)

Let's start by expanding the expression:

(2k + 3)(2k + 5)(2k + 7)...(4k + 3)

Notice that this expression is simply the previous expression multiplied by (4k + 1) and (4k + 3) and divided by (2k + 1).

Using the inductive hypothesis, we know that the previous expression is equal to a function of k. Therefore, the entire expression can be represented as a function of (k+1) as well.

Conclusion: We have successfully demonstrated that the expression holds true for the base case and that assuming its truth for an arbitrary k leads to its truth for k+1. Therefore, by the principle of mathematical induction, the expression (2n+1)(2n+3)(2n+5)...(4n-1) is equal to a function of n.

Important Note: This proof does not explicitly provide the exact function of n that the expression is equal to. Finding that function would require further exploration and possibly utilizing other mathematical techniques.

Related Post