Math Problem Statement

Question content area top Part 1 Write an explicit and a recursive formula for the sequence. 4​, 11​, 18​, 25​, 32​, ... Question content area bottom Part 1 Write an explicit formula. a Subscript nequals    enter your response here ​(Simplify your​ answer.) Part 2 Write a recursive formula. a Subscript n equals    enter your response here ​(Simplify your​ answer.) a 1 equals    enter your response here

Solution

To solve this, we need to identify the pattern in the sequence and derive both explicit and recursive formulas.

Given Sequence:

4, 11, 18, 25, 32, ...

Step 1: Identify the Pattern

The difference between consecutive terms is constant:

  • 114=711 - 4 = 7
  • 1811=718 - 11 = 7
  • 2518=725 - 18 = 7
  • 3225=732 - 25 = 7

The sequence is an arithmetic sequence with a common difference (dd) of 77.


Part 1: Explicit Formula

The explicit formula for an arithmetic sequence is: an=a1+(n1)da_n = a_1 + (n - 1) \cdot d Where:

  • a1=4a_1 = 4 (the first term),
  • d=7d = 7 (the common difference),
  • nn is the term number.

Substituting values: an=4+(n1)7a_n = 4 + (n - 1) \cdot 7

Simplify: an=4+7n7a_n = 4 + 7n - 7 an=7n3a_n = 7n - 3

Explicit Formula: an=7n3a_n = 7n - 3


Part 2: Recursive Formula

The recursive formula for an arithmetic sequence is: an=an1+da_n = a_{n-1} + d Where:

  • d=7d = 7 (the common difference),
  • a1=4a_1 = 4 (the first term).

Recursive Formula: an=an1+7for n2a_n = a_{n-1} + 7 \quad \text{for } n \geq 2 a1=4a_1 = 4


Final Answer:

  1. Explicit Formula: an=7n3a_n = 7n - 3

  2. Recursive Formula: an=an1+7,a1=4a_n = a_{n-1} + 7, \quad a_1 = 4

Let me know if you want a more detailed explanation or examples!

Related Questions:

  1. What is the 10th term of this sequence?
  2. How do you derive the explicit formula for a general arithmetic sequence?
  3. How does the common difference affect the shape of the sequence graph?
  4. What happens if the sequence starts with a different first term?
  5. Can you represent this sequence graphically?

Tip:

Always verify your formulas by plugging in the first few terms of the sequence to ensure they match!

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Math Problem Analysis

Mathematical Concepts

Arithmetic Sequences
Algebra

Formulas

Explicit formula for arithmetic sequence: a_n = a_1 + (n - 1) * d
Recursive formula for arithmetic sequence: a_n = a_(n-1) + d

Theorems

Arithmetic Sequence Properties

Suitable Grade Level

Grades 7-10