Math Problem Statement

Prove that the product of two integers, one of the form 3 π‘˜ 1 + 2 and the other of the form 3 π‘˜ 2 + 2 , where π‘˜ 1 and π‘˜ 2 are integers, is of the form 3 π‘˜ 3 + 1 for some integer π‘˜ 3 .

Solution

To prove that the product of two integers, one of the form 3k1+23k_1 + 2 and the other of the form 3k2+23k_2 + 2, where k1k_1 and k2k_2 are integers, is of the form 3k3+13k_3 + 1 for some integer k3k_3, we can proceed as follows:

Let: a=3k1+2a = 3k_1 + 2 b=3k2+2b = 3k_2 + 2

We want to show that: ab=(3k1+2)(3k2+2)ab = (3k_1 + 2)(3k_2 + 2) is of the form 3k3+13k_3 + 1 for some integer k3k_3.

First, compute the product abab: ab=(3k1+2)(3k2+2)ab = (3k_1 + 2)(3k_2 + 2)

Expanding this product using the distributive property: ab=3k1β‹…3k2+3k1β‹…2+2β‹…3k2+2β‹…2ab = 3k_1 \cdot 3k_2 + 3k_1 \cdot 2 + 2 \cdot 3k_2 + 2 \cdot 2

Simplify each term: ab=9k1k2+6k1+6k2+4ab = 9k_1k_2 + 6k_1 + 6k_2 + 4

Next, factor out the common factor of 3 from the first three terms: ab=3(3k1k2+2k1+2k2)+4ab = 3(3k_1k_2 + 2k_1 + 2k_2) + 4

Now, let k3=3k1k2+2k1+2k2k_3 = 3k_1k_2 + 2k_1 + 2k_2. Notice that k3k_3 is an integer since k1k_1 and k2k_2 are integers.

Thus, we can write: ab=3k3+4ab = 3k_3 + 4

We need to show that 3k3+43k_3 + 4 is of the form 3k3+13k_3 + 1. To do this, we recognize that 4 can be written as: 4=3+14 = 3 + 1

Therefore: ab=3k3+3+1ab = 3k_3 + 3 + 1

Combine like terms: ab=3(k3+1)+1ab = 3(k_3 + 1) + 1

Let k3β€²=k3+1k_3' = k_3 + 1. Notice that k3β€²k_3' is also an integer since k3k_3 is an integer. Hence, we have: ab=3k3β€²+1ab = 3k_3' + 1

Thus, the product abab is indeed of the form 3k3β€²+13k_3' + 1 for some integer k3β€²k_3'.

This completes the proof.

Would you like more details or have any questions?

Here are some related questions for further exploration:

  1. What is the product of 3k1+13k_1 + 1 and 3k2+23k_2 + 2?
  2. How do the properties of modular arithmetic apply to this problem?
  3. Can you prove similar results for numbers of the form nk+mnk + m?
  4. How does this result relate to polynomial congruences?
  5. What other properties of numbers of the form 3k+23k + 2 can be derived?
  6. How does the distributive property facilitate this proof?
  7. Can you prove the result using induction?
  8. How does this relate to quadratic residues in number theory?

Tip: When proving statements involving integers, consider using properties of modular arithmetic to simplify and solve the problem efficiently.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Number Theory
Modular Arithmetic

Formulas

Distributive Property

Theorems

-

Suitable Grade Level

Advanced High School