The sequence $6,-9,x,y$ is such that the first three terms form an arithmetic sequence and the last three terms form a geometric sequence. Find $x$ and $y$.
Express your answer as $x,y$.
There is no 6 terms, so assuming that 6 is the first term we know x = -34, now what would y be if it is now geometric?
Well, one possibility would be:
6, - 9, -24, -64
The first 3 form an arithmetic sequence with -15 as the common difference, and the last 3 form a geometric sequence with a common ratio of 2 2/3.