Math Problem Statement
Solution
This problem involves solving for the number of terms in a geometric sequence. Let's solve it step by step:
Given:
- The first term () is 4.
- The sum of all terms () is .
- The common ratio () is .
- The formula for the sum of a geometric sequence:
Step 1: Substitute known values
Using the formula for the sum of the sequence:
Simplify the denominator:
Cancel the 4:
Rearrange to isolate :
Step 2: Solve for
Take the logarithm of both sides or solve by inspection:
Since the base is , must be 10 because the powers of alternate signs. Here, the result matches the positive side.
Final Answer:
Let me know if you’d like further clarification or verification!
Related Questions:
- How would the solution change if the common ratio were positive?
- Can this method be generalized for other common ratios?
- What happens if the sum is positive but is negative?
- How would the formula change for an infinite geometric sequence?
- What practical applications use geometric sequences with negative ratios?
Tip:
When solving equations involving powers, logarithms can simplify the process—especially when isn't an integer.
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Math Problem Analysis
Mathematical Concepts
Geometric Sequences
Exponential Equations
Formulas
Sum of a finite geometric sequence Sn = a(1 - r^n) / (1 - r) for r ≠ 1
Theorems
Laws of Exponents
Suitable Grade Level
Grades 10-12
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