Math Problem Statement

The sequence in the box shows the number of text messages Karis sends each week for four consecutive weeks: 4, 8, 16, 32,... Which formula could be used to determine the number of text messages Karis will send next week (an+1) if the number of text messages sent this week (an) is known?

Solution

The sequence shown is 4,8,16,32,4, 8, 16, 32, \ldots, which appears to be a geometric sequence where each term is multiplied by 2 to get the next term.

Given this information, let's evaluate each option to find the correct recursive formula:

  1. an+1=12ana_{n+1} = \frac{1}{2} a_n: This would mean each term is half of the previous term, which does not match our sequence.

  2. an+1=2×an+4a_{n+1} = 2 \times a_n + 4: This suggests each term is double the previous term plus 4, which also does not fit the pattern.

  3. an+1=an+4a_{n+1} = a_n + 4: This would imply an arithmetic sequence where each term increases by 4, which does not match our geometric sequence.

  4. an+1=an×2a_{n+1} = a_n \times 2: This correctly describes the relationship, as each term is double the previous term.

The correct answer is: an+1=an×2a_{n+1} = a_n \times 2

Would you like further details or have any questions?

Here are some related questions for further exploration:

  1. What is a geometric sequence, and how does it differ from an arithmetic sequence?
  2. How can you find the general formula for a geometric sequence?
  3. What would happen if the common ratio was a fraction instead of 2?
  4. How would you determine the 10th term in this sequence?
  5. What are real-world examples of exponential growth similar to this sequence?

Tip: In a geometric sequence, each term is obtained by multiplying the previous term by a constant called the common ratio.

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Math Problem Analysis

Mathematical Concepts

Sequences
Geometric Sequence

Formulas

an+1 = an * r (where r is the common ratio in a geometric sequence)

Theorems

Geometric Sequence Formula

Suitable Grade Level

Grade 8-10