Math Problem Statement
The third term of a geometric progression is -108 and the sixth term is 32. Find i) The common ratio and the first term.
ii) Geometric sequence
iii) 10th term
Solution
Given that the third term of a geometric progression (GP) is and the sixth term is , we are to find the common ratio, the first term, and other related details.
Step 1: Find the Common Ratio (r)
Let's denote the first term by and the common ratio by . The th term of a geometric sequence can be expressed as:
For the third term ():
For the sixth term ():
We now have two equations:
Step 2: Solve for the Common Ratio (r)
Divide Equation 2 by Equation 1:
Simplifying:
Thus,
So, the common ratio is .
Step 3: Find the First Term (a)
Using the value of in Equation 1:
Substitute :
Multiply both sides by :
So, the first term is .
Step 4: Write the Geometric Sequence
With and , the first few terms of the geometric sequence are:
- First term:
- Second term:
- Third term:
- Fourth term:
- Fifth term:
- Sixth term:
So, the geometric sequence is:
Step 5: Find the 10th Term
To find the 10th term ():
Substitute and :
Since is negative, we get:
Would you like any further details or have any questions? Here are some related questions:
- What is the general formula for the th term of a geometric sequence?
- How do you find the sum of the first terms in a geometric series?
- How would the sequence change if the common ratio was a positive number?
- What happens if the common ratio is a fraction greater than 1?
- How can you determine if a sequence is geometric based on the terms provided?
Tip: When working with geometric sequences, it's important to consider whether the common ratio is positive or negative, as this will affect the sign of the terms in the sequence.
Ask a new question for Free
By Image
Drop file here or Click Here to upload
Math Problem Analysis
Mathematical Concepts
Geometric Progression
Common Ratio
Nth Term Formula
Formulas
Nth term of a geometric sequence formula: T_n = a * r^(n-1)
Theorems
-
Suitable Grade Level
Grades 9-12
Related Recommendation
Finding the Common Ratio and Sum of a Geometric Series
Solving a GP Problem: Finding the First Term Given Two Terms
Solve the Arithmetic and Geometric Progression Series
Finding the 10th Term of an Arithmetic or Geometric Progression
Solving Geometric Progression Problems - Common Ratio, Nth Term, and Sum