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If f(1)=1 and f(n)=4f(n-1) what is the value of f(4)?

Sagot :

Answer:

  64

Step-by-step explanation:

You have the recursive formula f(1)=1; f(n)=4f(n-1) and you want f(4).

Recursion

The value of f(4) can be found a couple of ways. Perhaps the simplest is to compute the first 4 terms of the sequence using the recursive formula.

  f(1) = 1

  f(2) = 4·1 = 4

  f(3) = 4·4 = 16

  f(4) = 4·16 = 64

The value of f(4) is 64.

Explicit formula

The multiplying factor of 4 on the previous term tells you this is a geometric sequence with a common ratio of 4. The explicit formula is then ...

  f(n) = f(1)·r^(n-1) . . . . . n-th term of sequence with common ratio r

  f(n) = 1·4^(n-1) . . . . . . formula for f(1)=1 and r=4

For n=4, this is ...

  f(4) = 1·4^(4-1) = 4^3

  f(4) = 64