SOLUTION: Find the nth term formula for the given arithmetic sequence; 9,7,5,3....

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Question 339231: Find the nth term formula for the given arithmetic sequence; 9,7,5,3....
Answer by alanc(27) About Me  (Show Source):
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look at each term: from 9 to 7 we see a difference of -2
from 7 to 5 we see a difference of -2
Therefore the common difference d = -2
first term a = 9
nth term should be describe as a_n = a + d*(n-1)
formula : a_n = 9 + -2*(n-1)
makes sense because the 2nd term 7 = 9 -2 *(2-1) = 7
try it out.