Math Problem Statement

Given the sequence -14, -6, -2, 0, 1, ..., find the recursive formula.

A. a1=−14�1=−14 and an+1=10an+6��+1=10��+6

B. a1=−14�1=−14 and an+1=2+an2��+1=2+��2

C. a1=−14�1=−14 and an+1=an+n��+1=��+�

D. a1=−14�1=−14 and an+1=nan

Solution

To determine which of the given options correctly represents the recursive formula for the sequence 14,6,2,0,1,-14, -6, -2, 0, 1, \dots, we can test each formula to see which one generates the sequence correctly.

Given sequence: 14,6,2,0,1,-14, -6, -2, 0, 1, \dots

Option A: a1=14a_1 = -14 and an+1=10an+6a_{n+1} = 10a_n + 6

  • a1=14a_1 = -14
  • a2=10(14)+6=140+6=134a_2 = 10(-14) + 6 = -140 + 6 = -134 (this does not match the sequence)

This option is incorrect.

Option B: a1=14a_1 = -14 and an+1=2+an2a_{n+1} = \frac{2 + a_n}{2}

  • a1=14a_1 = -14
  • a2=2+(14)2=122=6a_2 = \frac{2 + (-14)}{2} = \frac{-12}{2} = -6
  • a3=2+(6)2=42=2a_3 = \frac{2 + (-6)}{2} = \frac{-4}{2} = -2
  • a4=2+(2)2=02=0a_4 = \frac{2 + (-2)}{2} = \frac{0}{2} = 0
  • a5=2+02=22=1a_5 = \frac{2 + 0}{2} = \frac{2}{2} = 1

This matches the given sequence, so this option is correct.

Option C: a1=14a_1 = -14 and an+1=an+na_{n+1} = a_n + n

  • a1=14a_1 = -14
  • a2=14+1=13a_2 = -14 + 1 = -13 (this does not match the sequence)

This option is incorrect.

Option D: a1=14a_1 = -14 and an+1=n×ana_{n+1} = n \times a_n

  • a1=14a_1 = -14
  • a2=1×(14)=14a_2 = 1 \times (-14) = -14 (this does not match the sequence)

This option is incorrect.

Conclusion:

The correct answer is Option B: a1=14a_1 = -14 and an+1=2+an2a_{n+1} = \frac{2 + a_n}{2}.

Would you like to delve into the derivation of this formula, or do you have any other questions?


Here are some related questions to explore:

  1. How can you generalize the method used to find this recursive formula for other sequences?
  2. What would the explicit formula for this sequence look like?
  3. How would the sequence change if the initial term a1a_1 was different?
  4. Can you identify other sequences that follow a similar recursive pattern?
  5. How can you check if a sequence is arithmetic or geometric?
  6. What happens to this sequence as nn becomes very large?
  7. Can you derive a closed-form expression for this sequence?
  8. What is the importance of the initial condition in recursive sequences?

Tip: When dealing with recursive sequences, it's often helpful to calculate the first few terms to see if the pattern matches the given sequence.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Recursive Sequences

Formulas

Recursive formula

Theorems

-

Suitable Grade Level

Grades 10-12