Math Problem Statement

find the seventh term of the sequence negative 5, 15, negative 45

Solution

The sequence provided is: 5,15,45,-5, 15, -45, \dots.

To find the seventh term, we first need to determine the pattern or rule governing the sequence. This sequence appears to be a geometric sequence where each term is multiplied by a common ratio to obtain the next term.

Step 1: Identify the common ratio

The common ratio rr can be found by dividing the second term by the first term: r=155=3r = \frac{15}{-5} = -3 Thus, each term is multiplied by 3-3 to get the next term.

Step 2: Use the formula for the nnth term of a geometric sequence

The formula for the nnth term ana_n of a geometric sequence is: an=a1rn1a_n = a_1 \cdot r^{n-1} Where:

  • a1a_1 is the first term,
  • rr is the common ratio, and
  • nn is the term number.

Step 3: Calculate the seventh term

For the seventh term (n=7n = 7): a7=5(3)71a_7 = -5 \cdot (-3)^{7-1} a7=5(3)6a_7 = -5 \cdot (-3)^6

Step 4: Evaluate the power

(3)6=729(-3)^6 = 729 a7=5729=3645a_7 = -5 \cdot 729 = -3645

So, the seventh term of the sequence is 3645-3645.

Would you like details on how I calculated this or have any questions?

Here are 5 questions related to the topic:

  1. How do you determine if a sequence is arithmetic or geometric?
  2. What is the formula for finding the sum of the first nn terms in a geometric sequence?
  3. Can a sequence have a common ratio of zero?
  4. How do you solve for an unknown term in an arithmetic sequence?
  5. What happens to a geometric sequence if the common ratio is a fraction?

Tip: Always check whether a sequence is arithmetic or geometric by examining the difference or ratio between consecutive terms.

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Math Problem Analysis

Mathematical Concepts

Geometric Sequences

Formulas

Formula for the nth term of a geometric sequence

Theorems

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Suitable Grade Level

High School