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Determine whether the sequence 15,13,11,9 is an arithmetic sequence if yes, identify the common difference.

User Mikael Gidmark
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1 Answer

11 votes
11 votes

The sequence is not an arithmetic sequence because. The n-term for an arithmetic sequence is:


a_n\text{ = }a_1\text{ + }(n-1)d

where d is the difference between two consecutive numbers. In this case d = 2. Because

15-13 = 2

13-11 = 2

11- 9 = 2

now, the first term for 15,13,11,9 is 15 = a_1, the second term would be:


a_2\text{ = }a_1\text{ + }(2-1)d\text{ }

that is equivalent to say:


a_2\text{ = 15 + }(2)2=19\\e13\text{ }

So we can conclude that 15,13,11,9 is not an arithmetic sequence.

User Alan Kazbekov
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