Question
\#1. The first five terms of a pattern are shown. \( 10,20,40,80 \) The equation \( S_{n}=a(b)^{n} \) can be used to calculate the value, \( S_{n} \), of any term, \( n \), in the pattern. NOTE - this is EXPONENTIAL (not a geometric sequence formula) What is the value of \( a \) in the equation? What is the value of \( b \) in the equation? What is the value of \( S_{6} \) ?
Ask by Williams Joseph. in the United States
Mar 07,2025
Upstudy AI Solution
Tutor-Verified Answer
Answer
\( a = 5 \), \( b = 2 \), and \( S_{6} = 320 \).
Solution
Below is a step-by-step solution:
---
**Step 1. Write the given pattern and formula**
We are given the first few terms of the pattern:
\[
10,\quad 20,\quad 40,\quad 80, \dots
\]
and the exponential formula:
\[
S_{n} = a(b)^{n}
\]
---
**Step 2. Identify the value of \( b \)**
Since each term is obtained by multiplying the previous term by a constant, we compare the ratio of consecutive terms. For example,
\[
\frac{S_{2}}{S_{1}} = \frac{20}{10} = 2
\]
Thus,
\[
b = 2.
\]
---
**Step 3. Determine the value of \( a \)**
Using the first term, where \( S_{1} = 10 \), we substitute \( n = 1 \) into the formula:
\[
S_{1} = a(b)^{1} = a \cdot b.
\]
Substitute the known values:
\[
10 = a \cdot 2.
\]
Solve for \( a \):
\[
a = \frac{10}{2} = 5.
\]
---
**Step 4. Calculate \( S_{6} \)**
Now that we have found \( a = 5 \) and \( b = 2 \), we substitute these into the formula to find the sixth term:
\[
S_{6} = 5 \cdot 2^{6}.
\]
Since
\[
2^6 = 64,
\]
we have
\[
S_{6} = 5 \cdot 64 = 320.
\]
---
**Final Answers:**
- The value of \( a \) is \( \boxed{5} \).
- The value of \( b \) is \( \boxed{2} \).
- The value of \( S_{6} \) is \( \boxed{320} \).
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Beyond the Answer
To identify the values of \( a \) and \( b \) in the equation \( S_{n} = a(b)^{n} \) based on the provided pattern \( 10, 20, 40, 80 \), we can see that the first term (when \( n = 1 \)) is \( S_{1} = 10 \). Therefore, \( a = 10 \). The pattern shows that each term doubles, indicating \( b = 2 \). Now, to find \( S_{6} \), we plug \( n = 6 \) into the equation: \[ S_{6} = 10(2)^{6} = 10 \times 64 = 640. \] So, the value of \( S_{6} \) is \( 640 \).