Proving Sn=(-1)^n(n+1) for Induction | Homework Solution

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In summary, the conversation discusses the equation Sn=1-3+5-7...+(-1)^n(2n+1) and the attempt at a solution to show that Sn=(-1)^n(n+1). It is mentioned that the proof is not complete as it does not show that it is true for n=1. However, the speaker believes that the proof is correct based on calculations for n=1, 2, and 3.
  • #1
mtayab1994
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Homework Statement



Sn=1-3+5-7...+(-1)^n(2n+1)

Homework Equations



Show that Sn=(-1)^n(n+1)

The Attempt at a Solution



S(n+1)=Sn+(-1)^(n+1)*(2n+3) = (-1)^n*(n+1)+ (-1)^(n+1)*(2n+3)
S(n+1)= (-1)^(n+1)*[(2n+3)-(n+1)] (because (-1)^(n+1)= - (-1)^n )
S(n+1)=(-1)^(n+1)*(n+2)

is that correct proof
 
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  • #2
Well, you haven't shown that it is true for n= 1, so, no. But that is easily fixed.
 
  • #3
HallsofIvy said:
Well, you haven't shown that it is true for n= 1, so, no. But that is easily fixed.

i did that before doing the work and for n=1 it came out to equal -3 and i also had to count S2 and S3 and i got 5 for S2 and -7 for S3.

But my proof is fine right?
 

FAQ: Proving Sn=(-1)^n(n+1) for Induction | Homework Solution

What is the concept of mathematical induction?

Mathematical induction is a method of mathematical proof used to prove that a statement or property holds for all natural numbers. It involves proving a base case and then using a logical argument to show that if the statement holds for any given number, it also holds for the next number.

How do you use mathematical induction to prove a statement?

To prove a statement using mathematical induction, you must first prove that it is true for the first or smallest natural number. This is known as the base case. Then, you must show that if the statement holds for any given natural number, it also holds for the next number. This is known as the inductive step. By repeating this process, you can prove that the statement holds for all natural numbers.

What is the statement that needs to be proved using mathematical induction in this homework solution?

The statement that needs to be proved is Sn=(-1)^n(n+1), where Sn represents a sequence of numbers starting at n=1 and going up to n=k.

How does the solution use mathematical induction to prove the statement?

The solution uses mathematical induction by first proving the base case, which is when n=1. Then, it shows that if the statement holds for any given number n=k, it also holds for the next number n=k+1. This completes the inductive step and proves that the statement holds for all natural numbers.

What is the significance of proving Sn=(-1)^n(n+1) for Induction?

Proving Sn=(-1)^n(n+1) for Induction is significant because it shows that the statement holds for all natural numbers. This can be used in various mathematical proofs and applications, as well as in understanding the patterns and properties of sequences. It also demonstrates the power and usefulness of mathematical induction as a proof technique.

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