Math Problem Statement

Find the first term and common difference of an arithmetic sequence given that a_3 = 8 and a_6 = 29/4.

Solution

From the image, the problem provides two terms of a sequence:

  • a3=8a_3 = 8
  • a6=294a_6 = \frac{29}{4}

This likely refers to an arithmetic or geometric sequence, where we need to find further terms, the common difference (in arithmetic sequences), or the common ratio (in geometric sequences), or determine the formula for the sequence.

Let's first assume it's an arithmetic sequence, which follows the form: 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, nn is the term number, and dd is the common difference.

We have two equations from the given terms:

  1. a3=a1+2d=8a_3 = a_1 + 2d = 8
  2. a6=a1+5d=294a_6 = a_1 + 5d = \frac{29}{4}

We can solve these equations to find a1a_1 and dd. Let's proceed with that.

Step 1: Express a1a_1 in terms of dd from the first equation: a1=82da_1 = 8 - 2d

Step 2: Substitute into the second equation: 82d+5d=2948 - 2d + 5d = \frac{29}{4} 8+3d=2948 + 3d = \frac{29}{4}

Step 3: Solve for dd: First, subtract 8 from both sides: 3d=2948=294324=343d = \frac{29}{4} - 8 = \frac{29}{4} - \frac{32}{4} = -\frac{3}{4} Now, divide both sides by 3: d=34×13=14d = -\frac{3}{4} \times \frac{1}{3} = -\frac{1}{4}

Step 4: Find a1a_1: Substitute d=14d = -\frac{1}{4} into a1=82da_1 = 8 - 2d: a1=82(14)=8+12=162+12=172a_1 = 8 - 2\left(-\frac{1}{4}\right) = 8 + \frac{1}{2} = \frac{16}{2} + \frac{1}{2} = \frac{17}{2}

So, the sequence is an arithmetic sequence with:

  • First term a1=172a_1 = \frac{17}{2}
  • Common difference d=14d = -\frac{1}{4}

If you need more details or clarifications, let me know!

Related Questions:

  1. What is the formula for the nn-th term of this arithmetic sequence?
  2. How do you find the sum of the first nn terms in an arithmetic sequence?
  3. What is the 10th term of this sequence?
  4. Can you show how to solve this if it were a geometric sequence instead of arithmetic?
  5. How does the common difference affect the behavior of the sequence?

Tip: Always double-check if a sequence is arithmetic or geometric by testing the ratio or difference between consecutive terms!

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Math Problem Analysis

Mathematical Concepts

Arithmetic Sequence
Algebra

Formulas

a_n = a_1 + (n-1) * d

Theorems

Formula for the n-th term of an arithmetic sequence

Suitable Grade Level

Grades 9-11