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| Math Central | Quandaries & Queries |
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Question from Justin, a student: Which expression can be used to find the nth term in this sequence? Please explain how to get the correct answer. I think it is A. but I am not sure, |
Hi Justin,
I think the choices should be
A. $-19n+113$ B. $-21n+115$ C. $19n+75$ D. $21n+73$
I tried $n = 1$ for each of the four expressions and got
A. $-19 \times 1 +113 = 94$ B. $-21 \times 1 +115 = 94$ C. $19 \times 1 +75 = 94$ D. $21 \times 1+73 =94$
Thus all four expressions yield $94$ when $n = 1.$ Next try $n = 2.$ Does each expression give $75?$ If any expression doesn't yield $75$ then that expression isn't correct.
Penny
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