SOLUTION: Need rule for nth term - HELP!!! Okay 1/2,3,11/2,8,21/2.... what is the rule for the nth term d = -12 and a1 (1 is subscrpt) =80 - what is the rule for the nth term not sure

Algebra ->  Sequences-and-series -> SOLUTION: Need rule for nth term - HELP!!! Okay 1/2,3,11/2,8,21/2.... what is the rule for the nth term d = -12 and a1 (1 is subscrpt) =80 - what is the rule for the nth term not sure       Log On


   

Question 100069: Need rule for nth term - HELP!!!
Okay
1/2,3,11/2,8,21/2.... what is the rule for the nth term
d = -12 and a1 (1 is subscrpt) =80 - what is the rule for the nth term
not sure of my answers
Thanks
Answer by Adam(64) About Me  (Show Source):
You can put this solution on YOUR website!
1/2,3,11/2,8,21/2...
Since most of the terms are in "halves". Good way how to start this problem is by coverting the integers in it into halves.It's generally good to have 1 type of numbers in pronlem either integers or fractions etc...
So 3 = 3*2/2 and 8= 8*2/2 , thus 3 = 6/2 and 8 = 16/2 and we get 1/2 , 6/2 , 11/2 , 16/2 , 21/2 ...Easy to see that every numerator is increased by 5.
It is arithmetic sequence. Formula for n-th term of arithmetic sequence is A%5Bn%5D=+A1%2B%28n-1%29%2Ad where d is increment you want to add each time.
We can write : A%5Bn%5D=1%2F2%2B5%2F2%2A%28n-1%29 or A%5Bn%5D+=+%281%2B5%2A%28n-1%29%29%2F2
Concerning your second problem I am quite sure you'll be able to finish it yourself. Good luck!