Recurring Equations: Solving for T(n) with Mathematical Induction

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In summary, the conversation is about solving a recurrence with the given rule T(n) = T(n/7) + T(4n/5) + n for n > 35 and base case T(n) = constant for n ≤ 35. The participants are discussing whether this is a mathematical induction problem and how to handle cases where n is not a multiple of 7 or 4n is not a multiple of 5. They also question the validity of plugging in numbers to solve the equation.
  • #1
XodoX
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Homework Statement



Solve the recurrence: T(n) = T(n/7) + T(4n/5) + n for n > 35 with base case T(n) = constant for n ≤ 35.

Homework Equations


The Attempt at a Solution



Is this mathematical induction? No idea how to do this one.
 
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  • #2
You seem to be missing a "=". Where is it supposed to be?
 
  • #3
Hi XodoX, it does look like a recurrence, except, as HallsofIvy is pointing, the recurrence rule is missing.
Is this T(n+1)=T(n)+T(n/7)+T(4n/5)+n ? (T(36)=3c+35)
if it is, what when n is not a multiple of 7 and 4n is not a multiple of 4 ? we take the floor / ceiling ? do you have some context around this question ?

Cheers...
 
  • #4
Fixed it. Sorry, wrong button.
 
  • #5
Still, is 36/7=5 ? is 144/5=28 ?
just to make sure we are solving the right problem, do you have some context around this puzzle ?

Cheers...
 
  • #6
No, nothing else. So plug in numbers? But the equation does not hold up. I don't get it.
 
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1. How do I determine the initial conditions for a recurrence relation?

The initial conditions for a recurrence relation are the starting values for the sequence. These values are usually given in the problem or can be calculated using the recurrence relation itself. For example, if the recurrence relation is defined as f(n) = 2f(n-1) and the initial condition is f(0) = 1, then we can determine the initial condition for f(1) by plugging in n=0 into the recurrence relation: f(1) = 2f(0) = 2(1) = 2.

2. What is the difference between a linear and non-linear recurrence relation?

A linear recurrence relation is one where the next term in the sequence is a linear combination of previous terms. This means that the coefficients of the previous terms are constants. On the other hand, a non-linear recurrence relation is one where the next term in the sequence is not a linear combination of previous terms. This can include exponential terms or terms raised to a power.

3. How do I solve a recurrence relation using iteration?

To solve a recurrence relation using iteration, you need to plug in the initial conditions and use the recurrence relation to find the next term in the sequence. Repeat this process until you have the desired number of terms in the sequence or until you can see a pattern emerge. This method is useful for linear recurrence relations but may not work for non-linear ones.

4. Can I use a closed-form solution to solve any recurrence relation?

No, not all recurrence relations have a closed-form solution. Closed-form solutions are only possible for certain types of recurrence relations, such as linear ones with constant coefficients. In some cases, it may be possible to use generating functions or other mathematical techniques to find a closed-form solution, but this is not always the case.

5. How do I know if my solution to a recurrence relation is correct?

One way to check if your solution to a recurrence relation is correct is to plug in the initial conditions and see if it produces the correct sequence. Another way is to use mathematical induction to prove that your solution satisfies the recurrence relation for all values of n. Lastly, you can use computer programs or software to generate the sequence and compare it to your solution.

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