Proof by Induction - Divisibility Proofs

In summary, the conversation discusses the use of implication symbols in a proof by induction and how to correctly write and manipulate expressions. The main issue is the incorrect use of implication symbols and the need to show that the final expression has a factor of 6.
  • #1
odolwa99
85
0

Homework Statement



Q. Prove by induction that... (please see attachment).

Homework Equations





The Attempt at a Solution



The end result should be divisible by 6, but hasn't worked out for me. Can someone help me spot where I've gone wrong? Thank you.
 

Attachments

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  • #2
You are using implication symbols (==>) incorrectly. Most of the places you have them, you should be using "=".

As to your question,
7*7k + 4*4k + 1
= 7*7k + 7*4k + 7 - 3*4k - 6.

Can you show that the expression above has a factor of 6 in it?
 
  • #3
May I ask how you solved for...
7*7k + 7*4k + 7 - 3*4k - 6
from
7*7k + 4*4k + 1?
 
  • #4
odolwa99 said:
May I ask how you solved for...
7*7k + 7*4k + 7 - 3*4k - 6
from
7*7k + 4*4k + 1?
I didn't "solve" for it; I just rewrote the second expression in a different way. You should convince yourself that the two expressions are equal.
 

1. What is proof by induction?

Proof by induction is a mathematical technique used to prove that a statement is true for all natural numbers. It involves breaking down a problem into smaller cases and using a logical argument to show that the statement holds for each case, ultimately proving that it holds for all natural numbers.

2. How does proof by induction work?

Proof by induction works by first proving that the statement is true for the base case, typically when n = 1. Then, assuming that the statement is true for some arbitrary value of n, the goal is to prove that it is also true for n+1. By showing that the statement holds for both the base case and for n+1, it can be concluded that the statement is true for all natural numbers.

3. What are some common types of divisibility proofs using induction?

Some common types of divisibility proofs using induction include proving that a statement is true for all even or odd numbers, or for all multiples of a certain number. These types of proofs often involve using the fact that if a number is divisible by another number, then its multiples are also divisible by that number.

4. What are the steps to proving a divisibility statement using induction?

The steps to proving a divisibility statement using induction are as follows:
1. Prove that the statement is true for the base case (usually when n = 1).
2. Assume that the statement is true for some arbitrary value of n.
3. Use this assumption to prove that the statement is also true for n+1.
4. Conclude that the statement is true for all natural numbers by the principle of mathematical induction.

5. Why is proof by induction a powerful tool in mathematics?

Proof by induction is a powerful tool in mathematics because it allows us to prove that a statement is true for infinitely many cases (all natural numbers) by only considering a few specific cases. This saves time and effort compared to proving the statement for each individual case. Additionally, many mathematical theorems and properties can be proven using induction, making it a widely applicable technique.

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