Math Problem Statement

Find the 75th term of the arithmetic sequence -1, 15, 31, ...

Solution

To find the 75th term of an arithmetic sequence, we need to identify the first term and the common difference.

The arithmetic sequence is: 1,15,31,-1, 15, 31, \dots

Step 1: Identify the First Term (aa) and the Common Difference (dd)

  • The first term a=1a = -1.
  • The common difference dd can be calculated by subtracting the first term from the second term: d=15(1)=15+1=16d = 15 - (-1) = 15 + 1 = 16

Step 2: Use the Formula for the nnth Term of an Arithmetic Sequence

The nnth term of an arithmetic sequence is given by: an=a+(n1)da_n = a + (n - 1) \cdot d

We need the 75th term, so let n=75n = 75: a75=1+(751)16a_{75} = -1 + (75 - 1) \cdot 16 a75=1+7416a_{75} = -1 + 74 \cdot 16 a75=1+1184a_{75} = -1 + 1184 a75=1183a_{75} = 1183

Answer

The 75th term of the sequence is 1183.

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Here are some related questions for further practice:

  1. How do you find the sum of the first 75 terms in this sequence?
  2. What is the general formula for any term in this arithmetic sequence?
  3. How can we determine if a number is part of this arithmetic sequence?
  4. How would you find the common difference if only given non-consecutive terms?
  5. What is the 100th term of this sequence?

Tip: In an arithmetic sequence, once you know the first term and the common difference, you can calculate any term directly!

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Math Problem Analysis

Mathematical Concepts

Arithmetic Sequences
Algebra

Formulas

n-th term of an arithmetic sequence: a_n = a + (n - 1) * d

Theorems

Arithmetic Sequence Term Formula

Suitable Grade Level

Grades 9-11