How do I find the first term of a geometric sequence?

1 Answer
Nov 15, 2015


In geometric sequences there is a case of repeated multiplication

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So the sum of the first n terms of sequence is ;

#S_n =( a(1-r^n))/(1-r)#

Now given you know r n and the sum you find a by re arranging


If you re given the nth term then'

#a_n = ar^(n-1)#

You may often has to use both these equation to get to the answer