Math Problem Statement

Find the nth term of the arithmetic sequence -5, -7/2, -2, ....

Solution

In an arithmetic sequence, the nn-th term can be found using the formula:

an=a1+(n1)da_n = a_1 + (n - 1) \cdot d

where:

  • ana_n is the nn-th term,
  • a1a_1 is the first term,
  • dd is the common difference between consecutive terms.

Step 1: Identify the first term and the common difference.

From the sequence:

  • The first term a1=5a_1 = -5.
  • To find the common difference dd, subtract the first term from the second term: d=7/2(5)1=7/2+51=7/2+10/21=32d = \frac{-7/2 - (-5)}{1} = \frac{-7/2 + 5}{1} = \frac{-7/2 + 10/2}{1} = \frac{3}{2} So, the common difference d=32d = \frac{3}{2}.

Step 2: General formula for the nn-th term.

Using the formula for the nn-th term: an=a1+(n1)da_n = a_1 + (n - 1) \cdot d Substitute a1=5a_1 = -5 and d=32d = \frac{3}{2}: an=5+(n1)32a_n = -5 + (n - 1) \cdot \frac{3}{2} an=5+3(n1)2a_n = -5 + \frac{3(n - 1)}{2} an=5+3n32a_n = -5 + \frac{3n - 3}{2} an=102+3n32a_n = \frac{-10}{2} + \frac{3n - 3}{2} an=10+3n32a_n = \frac{-10 + 3n - 3}{2} an=3n132a_n = \frac{3n - 13}{2}

Thus, the general formula for the nn-th term of the sequence is: an=3n132a_n = \frac{3n - 13}{2}

Would you like further explanation or examples?

Here are five related questions:

  1. How do you derive the common difference in an arithmetic sequence?
  2. What happens to the nn-th term formula if the common difference is negative?
  3. How do you find the sum of the first nn terms of an arithmetic sequence?
  4. Can an arithmetic sequence have a variable common difference? Why or why not?
  5. What is the difference between arithmetic and geometric sequences?

Tip: The common difference in arithmetic sequences can be positive or negative, influencing whether the sequence increases or decreases.

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Math Problem Analysis

Mathematical Concepts

Arithmetic Sequence
Sequences and Series

Formulas

nth term formula for an arithmetic sequence: a_n = a_1 + (n - 1) * d

Theorems

Arithmetic Sequence Formula

Suitable Grade Level

Grades 8-10