Math Problem Statement

answer

Find the 12th term of the arithmetic sequence: -4x + 5, -10x + 2, -16x - 1, ...

Solution

The arithmetic sequence presented in the image is:

4x+5,10x+2,16x1,-4x + 5, -10x + 2, -16x - 1, \ldots

We are tasked with finding the 12th term of this sequence.

Step 1: Identify the First Term (a1a_1)

The first term of the sequence is:

a1=4x+5a_1 = -4x + 5

Step 2: Find the Common Difference (dd)

The common difference dd in an arithmetic sequence is the difference between any two consecutive terms.

Let's subtract the first term from the second term:

d=(10x+2)(4x+5)=10x+2+4x5=6x3d = (-10x + 2) - (-4x + 5) = -10x + 2 + 4x - 5 = -6x - 3

So, the common difference d=6x3d = -6x - 3.

Step 3: Use the Formula for the nn-th Term

The general formula for the nn-th term ana_n of an arithmetic sequence is:

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

To find the 12th term a12a_{12}, substitute n=12n = 12, a1=4x+5a_1 = -4x + 5, and d=6x3d = -6x - 3 into the formula:

a12=(4x+5)+(121)(6x3)a_{12} = (-4x + 5) + (12 - 1) \cdot (-6x - 3) a12=(4x+5)+11(6x3)a_{12} = (-4x + 5) + 11 \cdot (-6x - 3) a12=(4x+5)+(66x33)a_{12} = (-4x + 5) + (-66x - 33) a12=4x+566x33a_{12} = -4x + 5 - 66x - 33 a12=70x28a_{12} = -70x - 28

Final Answer:

The 12th term of the arithmetic sequence is:

a12=70x28a_{12} = -70x - 28

Would you like more details on any step, or do you have any questions?

Here are some related questions to consider:

  1. What is the general term of this arithmetic sequence?
  2. How do you find the sum of the first 12 terms of the sequence?
  3. What is the 20th term of this arithmetic sequence?
  4. How would the result change if xx is a specific number (e.g., x=2x = 2)?
  5. Can you derive the formula for any term of an arithmetic sequence?

Tip: In an arithmetic sequence, knowing the first term and common difference lets you calculate any term using a simple formula!

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Math Problem Analysis

Mathematical Concepts

Arithmetic Sequences
Algebra

Formulas

General term of arithmetic sequence: a_n = a_1 + (n-1) * d
Common difference: d = a_2 - a_1

Theorems

Arithmetic sequence formula

Suitable Grade Level

Grades 9-10