3rd to 5th is 2r distance, so r=1/2 (17-11)=3
given 5th , work back
17,14,11,8,5 so 5 is the first term.
20,23 are the remaining terms of the first seven, add them.
This type of sequence is also called arithmetic sequence, and there are formulas associated with it, and you ought to review them.
The fifth term of a linear sequence is 17 and the third term is 11, Find the sum of the first seven terms
2 answers
Pardon