Problem

Which term in the arithmetic sequence $9,4,-1, \ldots$ has the value $-146 ?$

Solution

Step 1 :Given the arithmetic sequence: \(9, 4, -1, \ldots\)

Step 2 :Find the common difference (d): \(d = 4 - 9 = -5\)

Step 3 :Use the formula for the nth term of an arithmetic sequence: \(a_n = a_1 + (n - 1)d\)

Step 4 :Plug in the given value for the nth term (\(-146\)) and the known values for \(a_1\) and d: \(-146 = 9 + (n - 1)(-5)\)

Step 5 :Solve for n: \(n = 32\)

Step 6 :\(\boxed{32}\) is the term number in the sequence with the value \(-146\)

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Source: https://solvelyapp.com/problems/30618/

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