Math Problem Statement

Simplify the expression P = ∏_{k=2}^n (1 - 1/k^2).

Solution

The problem you shared asks to simplify the expression P=k=2n(11k2)P = \prod_{k=2}^{n} \left( 1 - \frac{1}{k^2} \right), where the product is taken from k=2k = 2 to nn.

Let's begin by simplifying the individual term:

11k2=k21k2=(k1)(k+1)k21 - \frac{1}{k^2} = \frac{k^2 - 1}{k^2} = \frac{(k - 1)(k + 1)}{k^2}

Thus, the product becomes:

P=k=2n(k1)(k+1)k2P = \prod_{k=2}^{n} \frac{(k - 1)(k + 1)}{k^2}

We can break this into two products:

P=k=2n(k1)k×k=2n(k+1)kP = \prod_{k=2}^{n} \frac{(k - 1)}{k} \times \prod_{k=2}^{n} \frac{(k + 1)}{k}

These two products can now be written as telescoping products. Let's handle each product separately:

  1. For k=2nk1k\prod_{k=2}^{n} \frac{k - 1}{k}, the terms telescope to:

12×23×34××n1n=1n\frac{1}{2} \times \frac{2}{3} \times \frac{3}{4} \times \cdots \times \frac{n-1}{n} = \frac{1}{n}

  1. For k=2nk+1k\prod_{k=2}^{n} \frac{k + 1}{k}, the terms telescope to:

32×43×54××n+1n=n+12\frac{3}{2} \times \frac{4}{3} \times \frac{5}{4} \times \cdots \times \frac{n+1}{n} = \frac{n+1}{2}

Now, multiplying both simplified products together:

P=1n×n+12=n+12nP = \frac{1}{n} \times \frac{n+1}{2} = \frac{n+1}{2n}

Thus, the simplified expression for PP is:

P=n+12nP = \frac{n+1}{2n}

Would you like further clarification or details on any step?

Here are 5 related questions to expand the topic:

  1. How would the product change if the starting value of kk were different?
  2. What happens to PP as nn \to \infty?
  3. Can you generalize this product for different powers of kk?
  4. How does the result change if instead of k2k^2, the denominator had k3k^3?
  5. Can you apply similar methods to simplify sums instead of products?

Tip: Telescoping series and products are a powerful tool in simplifications, as many intermediate terms cancel out, leaving just a few terms from the beginning and end of the expression.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Algebra
Product Notation
Telescoping Products

Formulas

1 - 1/k^2 = (k^2 - 1)/k^2 = (k - 1)(k + 1)/k^2
∏_{k=2}^n ((k-1)(k+1)/k^2)
Telescoping product simplifications

Theorems

Telescoping Products
Algebraic Simplification

Suitable Grade Level

Grades 10-12