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2 votes
Please Help !! Sigma......what is the value of the

Please Help !! Sigma......what is the value of the-example-1
User Xni
by
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2 Answers

3 votes

Answer:

7

Explanation:

User AlexGH
by
8.2k points
2 votes
You have to count
\sum\limits_(i=1)^(3)\left(4\cdot \left((1)/(2)\right)^(i-1)\right).
For i=1,

4\cdot \left((1)/(2)\right)^(i-1)=4\cdot \left((1)/(2)\right)^(1-1)=4\cdot \left((1)/(2)\right)^(0)=4\cdot 1=4.
For i=2,

4\cdot \left((1)/(2)\right)^(i-1)=4\cdot \left((1)/(2)\right)^(2-1)=4\cdot \left((1)/(2)\right)^(1)=4\cdot(1)/(2)=2.
For i=3,

4\cdot \left((1)/(2)\right)^(i-1)=4\cdot \left((1)/(2)\right)^(3-1)=4\cdot \left((1)/(2)\right)^(2)=4\cdot (1)/(4)=1.
Then
\sum\limits_(i=1)^(3)\left(4\cdot \left((1)/(2)\right)^(i-1)\right) =4+2+1=7.
Answer: Correct choice is C.



User Kevin Gilbert
by
8.3k points

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