In a sequence, every term after the second term is twice the sum of the two following terms. The seventh term of the sequence is 8, and the ninth term is 24. What is the first term of the sequence?
2006-09-12 03:45:18 · 4 answers · asked by Anonymous in Education & Reference ➔ Homework Help
can anyone do this math problem? it is so hard and would help me out so much/
2006-09-12 09:23:48 · update #1
The sequence is as follows:
33.5 -24.5 18 -13 10 -6 8 4 24
To solve:
First realize that the the 7th + 8th = 24/2 = 12
Therefore, the 8th term = 4
Next:
The 6th + 7th = 4/2 = 2
Therefore, the 6th term = -6
Continue:
Working your way backwards to the first term.
2006-09-12 03:53:59 · answer #1 · answered by Will 4 · 1⤊ 0⤋
I think you wrote "two following terms" when you meant "two preceding terms". Then 24 would be twice the sum of the seventh and eighth terms, so 12 is the sum of the seventh and eighth terms; and 8 is the seventh term, so 4 must be the eighth term. Now you can work backwards to the sixth, fifth and so on. Some of the terms are going to be negative numbers.
If "following terms" is correct after all, then 8 is twice the sum of the eighth and ninth terms; so 4 is the sum of the eighth and ninth terms; and the ninth term is 24, so the eighth term must be (-20). Again, you can keep working backwards in the same way, and some of the terms will be negative.
2006-09-12 10:58:25 · answer #2 · answered by bh8153 7 · 1⤊ 0⤋
Question 15 with answer
cemc.uwaterloo.ca/english/contests/past_solution/2000/fermat.pdf
2006-09-12 10:56:14 · answer #3 · answered by god knows and sees else Yahoo 6 · 0⤊ 1⤋
-800
2006-09-12 11:00:24 · answer #4 · answered by nba07 1 · 0⤊ 1⤋