Question

Ivy and Andrey were asked to find an explicit formula for the sequence -100, -50,0,50, ...

Ivy said the formula is f(n) = -100 + 50(n-1).
Andrey said the formula is f(n) = -150 + 50n.
Which one of them is right?
Choose 1 answer:
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Only Ivy
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Only Andrey
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Both Ivy and Andrey
0
Neither Ivy nor Andrey
2 of 4
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Answer 1

Both Ivy and Andrey

Explanation:

-100, -50, 0, 50 is an arithmetic sequence, because it has a common difference:

-50 − (-100) = 50

0 − (-50) = 50

50 − 0 = 50

The first term is -100 and the common difference is 50, so:

f(n) = -100 + 50 (n − 1)

Simplifying:

f(n) = -100 + 50n − 50

f(n) = -150 + 50n

So both Ivy and Andrey are correct.