CPM Homework Help : A2C Problem 13-135

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13-135.

Each of the following sums is the beginning of an arithmetic series. Find the n^th term of each series, for the specified value of n.

$\left(−2\right) + \left(−5\right) + \left(−8\right) + …, n = 12$
Step 1 (a):
Set up an equation to describe the sequence.
$t\left(n\right) = −2 − 3\left(n − 1\right)$
Step 2 (a):
Now substitute 12 for n to find the 12th term.
$t\left(12\right) = −2 − 3\left(11\right)$
Answer (a):
− $35$

$9 + 15 + 21 + …, n = 20$
Hint (b):
See part (a).

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