SOLUTION: If f(1)=9 and f(n)=-3f(n-1)+n then find the value of f(5)

Algebra ->  Equations -> SOLUTION: If f(1)=9 and f(n)=-3f(n-1)+n then find the value of f(5)      Log On


   

Question 1198249: If f(1)=9 and f(n)=-3f(n-1)+n then find the value of f(5)
Found 2 solutions by ewatrrr, ikleyn:
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!

Hi  
f(n)=-3f(n-1)+ n
Given: f(1)= 9
f(2)=-3f(1)+ 2 = -25  Noted -3 coefficient
f(3) = -3f(2) + 3 = 75 + 3 = 78
f(4) = -3f(3) + 4 = -234 + 4 = -230
f(5) = -3f(4) + 5 = 690 + 5 = 695
Wish You the Best in your Studies.


Answer by ikleyn(52781) About Me  (Show Source):
You can put this solution on YOUR website!
.
If f(1)=9 and f(n)=-3f(n-1)+n then find the value of f(5)
~~~~~~~~~~~~~~


            Calculations made by @ewatrrr in her post all are incorrect.
            So I came to make it in a right way.
            Simply do it step by step. 


f(2) = -3f(1) + 2 = -3*9 + 2      =  -25

f(3) = -3f(2) + 3 = -3*(-25) + 3  =   78

f(4) = -3f(3) + 4 = -3*78 + 4     = -230

f(5) = -3f(4) + 5 = -3*(-230) + 5 =  695

Solved (correctly).

----------------

@ewatrrr re-wrote her post after seeing my calcs.