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arithematic sequence

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arithematic sequence

by LFalken » Tue Jun 16, 2009 9:36 am
In the arithmetic sequence t1, t2, t3........tn....t1=23 and tn = tn-1 -3 for each n>1. What is the value of n when tn=-4?




answer is = 10

Can someone explain this one to me? Thank you!
LFAL
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by p2pg » Tue Jun 16, 2009 10:27 am
If t1=23, then t2=t1-3=20...so the sequence will be
23,20,17,14,11,8,5,2,-1,-4

If tn=-4, then n=10
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by tohellandback » Tue Jun 16, 2009 8:37 pm
in an AP tn=a+(n-1)d
-4=23+(n-1)*(-3)
(n-1)=-27/-3
n=9+1=10
The powers of two are bloody impolite!!
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