Question #07e0c

1 Answer
Feb 4, 2018

Assumption: you mean the tenth term

#a_10->1/27xx3^(10-1) = 729#

Explanation:

First of all observe that #1/27<1/9<1/3 < ? " "#and so on.
So as we progress through the sequence the values are increasing

Notice the following:

#3xx3=9#
#3xx9=27#

So to progress from one term to the next the value of 3 in some format is involved.

Also notice that:

#1/27xx3=1/9#

#1/27xx3xx3=1/3#

Set the position in the sequence be designated as the #n^("th")# position.
Let the #n^("th")# term be designated as #a_n#

When #n=1# we are looking at the first place #a_1->1/27#
When #n=2# we are looking at the second place #a_2->1/9#

and so on. So putting this all together we have:

Note that #3^0=1=4^0=5^0# and so on

#a_n=a_1 ->1/27xx1 color(white)(---)->color(white)(---)1/27xx3^0#
#a_n=a_2->1/27xx3#
#a_n=a_3->1/27xx3xx3#

So by inspection we observe that for any #n>0# we have
#a_n=1/27xx3^(n-1)#

So #a_10->1/27xx3^(10-1) = 729#