Math Problem Statement

Find the indicated term for the geometric sequence. StartFraction negative 4 Over 243 EndFraction ​, StartFraction 4 Over 81 EndFraction ​, StartFraction negative 4 Over 27 EndFraction ​, ​...; the 6th term

Solution

To find the 6th term of the geometric sequence, we follow these steps:

Step 1: Identify the first term (aa) and common ratio (rr):

The sequence is: 4243,481,427,-\frac{4}{243}, \frac{4}{81}, -\frac{4}{27}, \dots

  1. The first term (aa) is: a=4243a = -\frac{4}{243}

  2. To find the common ratio (rr), divide the second term by the first term: r=4814243=4812434=3r = \frac{\frac{4}{81}}{-\frac{4}{243}} = \frac{4}{81} \cdot \frac{-243}{4} = -3

Step 2: Use the formula for the nn-th term of a geometric sequence:

The formula is: an=arn1a_n = a \cdot r^{n-1}

Here, n=6n = 6. Substituting the values of a=4243a = -\frac{4}{243}, r=3r = -3, and n=6n = 6: a6=4243(3)61a_6 = -\frac{4}{243} \cdot (-3)^{6-1}

Step 3: Simplify the exponent:

(3)61=(3)5=243(-3)^{6-1} = (-3)^5 = -243

Step 4: Calculate a6a_6:

a6=4243243a_6 = -\frac{4}{243} \cdot -243 a6=972243a_6 = \frac{972}{243} a6=4a_6 = 4

Final Answer:

The 6th term of the sequence is: 4\boxed{4}

Would you like further clarification or details on this solution?


Related Questions:

  1. How is the common ratio in a geometric sequence determined?
  2. What are the properties of a geometric sequence with alternating signs?
  3. Can you derive a general formula for the sum of the first nn terms of this sequence?
  4. How would the sequence change if the common ratio were positive?
  5. What are the applications of geometric sequences in real-world scenarios?

Tip:

Always double-check the common ratio calculation when solving geometric sequences to avoid sign errors!

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Sequences and Series
Geometric Sequences
Exponentiation

Formulas

nth term of a geometric sequence: a_n = a * r^(n-1)

Theorems

Properties of geometric sequences

Suitable Grade Level

Grades 9-12