Math Problem Statement

Find the 9th term of the arithmetic sequence −5x + 2, −11x − 3, −17x − 8, ...

Solution

To solve the problem and find the 9th term of the arithmetic sequence, we will analyze the given terms and calculate the common difference dd and apply the formula for the nth term:

The first few terms of the sequence are: 5x+2,11x3,17x8,-5x + 2, -11x - 3, -17x - 8, \dots

Step 1: Find the common difference dd

The common difference dd in an arithmetic sequence is calculated as: d=second termfirst termd = \text{second term} - \text{first term}

d=(11x3)(5x+2)d = (-11x - 3) - (-5x + 2)

Simplify: d=11x3+5x2d = -11x - 3 + 5x - 2

d=6x5d = -6x - 5

Step 2: General formula for the nnth term

The general formula for the nnth term of an arithmetic sequence is: an=a1+(n1)da_n = a_1 + (n-1) \cdot d where a1a_1 is the first term, dd is the common difference, and nn is the term number.

Here: a1=5x+2,d=6x5a_1 = -5x + 2, \quad d = -6x - 5

Step 3: Find the 9th term (n=9n = 9)

Substitute into the formula: a9=a1+(91)da_9 = a_1 + (9-1) \cdot d

a9=(5x+2)+8(6x5)a_9 = (-5x + 2) + 8 \cdot (-6x - 5)

Simplify: a9=5x+248x40a_9 = -5x + 2 - 48x - 40

a9=53x38a_9 = -53x - 38

Final Answer:

The 9th term of the sequence is: 53x38\boxed{-53x - 38}

Would you like more details or have further questions? Here are five related questions for exploration:

  1. What is the general formula for any term in this sequence?
  2. How can we verify that the common difference is consistent across the sequence?
  3. How would the formula change if the first term were different?
  4. What happens if xx has a specific value, e.g., x=2x = 2?
  5. How can we identify whether a sequence is arithmetic or not?

Tip: Always verify your calculated common difference dd by checking multiple consecutive terms to ensure consistency.

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Math Problem Analysis

Mathematical Concepts

Arithmetic Sequences
Linear Algebra

Formulas

Common difference formula: d = second term - first term
Nth term formula for arithmetic sequence: an = a1 + (n-1) * d

Theorems

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Suitable Grade Level

Grade 8-10