Proof by induction

  • Thread starter smh745
  • Start date
  • #1
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I need help to solve this problem

Use induction to prove that, for n>=0:

3*5^0 + 3*5^1 + 3*5^2 + 3*5^3 + ...+ 3*5^n = 3*(5^(n+1)-1)/4

in other word


n

[tex]\sum[/tex] 3*5 k= 3*(5 n+1-1) / 4
k= 0
 

Answers and Replies

  • #2
rock.freak667
Homework Helper
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Assume true for n=N and now prove true for n=N+1.
Do you know how to do a proof by induction?
 
  • #3
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I did these steps and I tried to complete the rest but I don't know some of the steps

and what I is in the attached doc.
 

Attachments

  • #4
rock.freak667
Homework Helper
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Try not to upload word documents as these usually contain viruses. Can you type out the steps you did?
 
  • #5
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Basis: n= 0
0
[tex]\sum [/tex]3*5^ 0 = 3

k= 0




3*(5 0+1-1) / 4 = 3




Assume:

n

[tex]\sum[/tex] 3*5^k= 3*(5 n+1-1) / 4
k= 0



Prove:

n+1

[tex]\sum[/tex] 3*5 ^k= 3*(5 (n+1)-1) / 4
k= 0


________________________________________
Proof:

n+1
[tex]\sum[/tex] 3*5^ k =

k= 0
 
  • #6
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0
As you have the base case, think about the sum:

3*5^0 + 3*5^1 + 3*5^2 + 3*5^3 + ...+ 3*5^n + 3*5^(n+1)

which is now your inductive step, as rock.freak667 suggested.

What are the two ways in which this can also be written with the information you already have?

The Bob
 

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