Answer:

Step-by-step explanation:
Given

Required
Determine the probability of 6 different lower case letters <em>(Question continuation)</em>
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There are 26 lower case letters.
The first can be any of letters 26
The second can be any of letters 26 - 1
The third can be any of letters 26 - 2
The fourth can be any of letters 26 - 3
The fifth can be any of letters 26 - 4
The sixth can be any of letters 26 - 5
Number of selection is:



The probability is:



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<em> --- approximated</em>
sub 2 for any "x"
3(2)^2-2(2)+1
6^2-4+1 i dont know if you need to simplify even more but if you do
36-4+1 32+1 31
i hope this helps you!
Notice that the above sequence is arithmetic because the common difference: d is constant.
d = second term - first term.
= 15 - 9
= 6
The general term of an arithmetic sequence is,
a_{n} =a_{1} +(n-1)d
Where , nth term = 
= First term
and d = common difference.
The given sequence is: 9, 15, 21, ...
Here a_{1} = 9,
d = 6
We need to find the 31st term. So, n = 31.
Next step is to plug in these values in the above formula. Therefore,

= 9 + 30* 6
= 9 + 180
= 189
So, 31st term of this sequence is 189.
Hope this helps you.