1) Use differences to find a pattern in the sequence. 4,4,9,20,38,64,99 Assuming that the pattern continues, the eighth term should be?
If you look at the difference between the terms, you get the following:
0, 5, 11, 18, 26, 35......
Now, see the difference between these new terms and you get:
5, 6, 7, 8, 9.......etc. It, therefore, follows that you will add: 10, 11, 12, 13......etc. to the FIRST differences: 35+10 =45, 45+11=56, 56+12=68.........etc. Therefore, your sequence will be:
4,4,9,20,38,64,99, 144, 200, 268........etc.
P.S. You could use this more complicated formula to generate each term:
a(n) = 1/6 (n^3 + 9n^2 - 34n + 48).
2) Use differences to find a pattern in the sequence. 6,9,20,39,66,101,144 Assuming that the pattern continues, the eighth term should be?
Do the same for this one and you will see these differences:
3, 11, 19, 27, 35, 43..............
Now look at the differences between these and you get a CONSTANT of 8. So, you will have:
43+8=51, 51+8=59, 59+8=67.........etc. So your sequence will be:
6,9,20,39,66,101,144, 195, 254, 321.........etc.
P.S. You could also use this more complicated formula to generate each term:
a(n) = 4n^2 - 9n + 11