SOLUTION: Please help me solve: Write the rule for the arithmetic series {{{a5=12}}} {{{d=5}}}

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Question 723418: Please help me solve: Write the rule for the arithmetic series a5=12 d=5
Answer by MathLover1(20855) About Me  (Show Source):
You can put this solution on YOUR website!

a rule for creating nth term formula: a%5Bn%5D=d%28n-1%29%2Ba%5B1%5D
given:
d=5
if we have a%5B5%5D=12, means n=5
12=5%285-1%29%2Ba%5B1%5D....find first term
12=25-5%2Ba%5B1%5D
12=20%2Ba%5B1%5D
12-20=a%5B1%5D
-8=a%5B1%5D.....first term
so, the nth term formula is:
a%5Bn%5D=5%28n-1%29-8
so, the arithmetic series:-8,-3,2,7,12....