Question

Which answer is the explicit rule for the sequence 11, 8.5, 6, 3.5, 1 ... ?

an=13.5+2.5n
an=13+2.5n
an=13.5−2.5n
an=13−1.5n

Answer 1

C.an=13.5−2.5n

Explanation:

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Answer 2

an=13.5−2.5n

Explanation:

To find the common difference

Take the end term and subtract the first term

8.5 -11 = -2.5

Take the third term and subtract the 3rd term to verify

6-8.5 = -2.5 check

The formula for an arithmetic sequence is

an = a1+d(n-1)

an = 11 -2.5(n-1)

Distribute

an = 11 -2.5n+2.5

Combine terms

an = 13.5 - 2.5n