SOLUTION: 7,9,-1,5, n what is n?

Algebra.Com
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
RELATED QUESTIONS

n+5(n-1)=7 What is n? (answered by sofiyac)
If n+7/9=1,then n is what? (answered by Ave)
n+5(n-1)=7 (answered by jim_thompson5910)
9+2(15+n)+7(n+5) (answered by jim_thompson5910)
if f(1)=9 and f(n)=-3f(n-1)+n then what is the value of... (answered by ikleyn)
what is 5 +... (answered by rfer)
N/9 x 3/4 = 5/12 what is n (answered by kekegeter )
1. A(n)=-3+(n-1)(5) 2. A(n)=-11+(n-1)(2) 3. A(n)=9+(n-1)(8) 4. A(n)=0.5+(n-1)(3.5) (answered by tommyt3rd)
1. A(n)=-3+(n-1)(5) 2. A(n)=-11+(n-1)(2) 3. A(n)=9+(n-1)(8) 4. A(n)=0.5+(n-1)(3.5) (answered by tommyt3rd)
1. A(n)=-3+(n-1)(5) 2. A(n)=-11+(n-1)(2) 3. A(n)=9+(n-1)(8) 4. A(n)=0.5+(n-1)(3.5) (answered by tommyt3rd)