Question

5

Which of the following is the result of expanding 22"-2,
n=1
O 8.5
O 15.5
O 32
60

Answer 1

Answer is B edg2021

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Answer 2

`\sum\limits^5_(n=1) {2^(n-2)} = 15.5`

Explanation:

Given

`\sum\limits^5_(n=1) {2^(n-2)`

Required

The result

To do this, we simply substitute 1 to 5 for n.

So, we have:

`\sum\limits^5_(n=1) {2^(n-2)} = 2^(1-2) + 2^(2-2) + 2^(3-2) + 2^(4-2) + 2^(5-2)`

`\sum\limits^5_(n=1) {2^(n-2)} = 2^(-1) + 2^(0) + 2^(1) + 2^(2) + 2^(3)`

Evaluate each exponent

`\sum\limits^5_(n=1) {2^(n-2)} = 0.5 + 1 + 2 + 4 +8`

`\sum\limits^5_(n=1) {2^(n-2)} = 15.5`