Question 1074938: 7,9,-1,5, n what is n?
Answer by Edwin McCravy(20056)   (Show Source):
You can put this solution on YOUR website! 7,9,-1,5, n what is n?
One of many possible general equations for a sequence that has
those first 4 terms is:
ax = (14x3-102x2+214x-105)/3
Substitute x=1
a1 = [14(1)3-102(1)2+214(1)-105]/3 =
[14(1)-102(1)+214(1)-105]/3 = [14-102+214-105]/3 =
21/3 = 7
Substitute x=2
a2 = [14(2)3-102(2)2+214(2)-105]/3 =
[14(8)-102(4)+214(2)-105]/3 = [112-408+428-105]/3 =
27/3 = 9
Substitute x=3
a3 = [14(3)3-102(3)2+214(3)-105]/3 =
[14(27)-102(9)+214(3)-105]/3 = [378-918+642-105]/3 =
-3/3 = -1
Substitute x=4
a4 = [14(4)3-102(4)2+214(4)-105]/3 =
[14(64)-102(16)+214(4)-105]/3 = [896-1632+856-105]/3 =
15/3 = 5
Substitute x=5
a5 = [14(5)3-102(5)2+214(5)-105]/3 =
[14(125)-102(25)+214(5)-105]/3 = [1750-2550+1070-105]/3 =
165/3 = 55
Answer: n = 55.
Edwin
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