Answer:
31
Step-by-step explanation:
The series are given as geometric series because these terms have common ratio and not common difference.
Our common ratio is 2 because:
1*2 = 2
2*2 = 4
The summation formula for geometric series (r ≠ 1) is:
[tex]\displaystyle \large{S_n=\frac{a_1(r^n-1)}{r-1}}[/tex] or [tex]\displaystyle \large{S_n=\frac{a_1(1-r^n)}{1-r}}[/tex]
You may use either one of these formulas but I’ll use the first formula.
We are also given that n = 5, meaning we are adding up 5 terms in the series, substitute n = 5 in along with r = 2 and first term = 1.
[tex]\displaystyle \large{S_5=\frac{1(2^5-1)}{2-1}}\\\displaystyle \large{S_5=\frac{2^5-1}{1}}\\\displaystyle \large{S_5=2^5-1}\\\displaystyle \large{S_5=32-1}\\\displaystyle \large{S_5=31}[/tex]
Therefore, the solution is 31.
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Summary
If the sequence has common ratio then the sequence or series is classified as geometric sequence/series.
Common Ratio can be found by either multiplying terms with common ratio to get the exact next sequence which can be expressed as [tex]\displaystyle \large{a_{n-1} \cdot r = a_n}[/tex] meaning “previous term times ratio = next term” or you can also get the next term to divide with previous term which can be expressed as:
[tex]\displaystyle \large{r=\frac{a_{n+1}}{a_n}}[/tex]
Once knowing which sequence or series is it, apply an appropriate formula for the series. For geometric series, apply the following three formulas:
[tex]\displaystyle \large{S_n=\frac{a_1(r^n-1)}{r-1}}\\\displaystyle \large{S_n=\frac{a_1(1-r^n)}{1-r}}[/tex]
Above should be applied for series that have common ratio not equal to 1.
[tex]\displaystyle \large{S_n=a_1 \cdot n}[/tex]
Above should be applied for series that have common ratio exactly equal to 1.
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Topics
Sequence & Series — Geometric Series
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Others
Let me know if you have any doubts about my answer, explanation or this question through comment!
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