SOLUTION: If f(1) = 3 and f(n)=-2f(n-1)+1, then f(5)= ? multiple choice options: -5,11, 21, 43 I tried plugging in f(1)=-2f(1-1)+1 but got 3= -2 (and they are obviously not equal). I a

Algebra ->  Functions -> SOLUTION: If f(1) = 3 and f(n)=-2f(n-1)+1, then f(5)= ? multiple choice options: -5,11, 21, 43 I tried plugging in f(1)=-2f(1-1)+1 but got 3= -2 (and they are obviously not equal). I a      Log On


   

Question 934993: If f(1) = 3 and f(n)=-2f(n-1)+1, then f(5)= ?
multiple choice options: -5,11, 21, 43
I tried plugging in f(1)=-2f(1-1)+1 but got 3= -2 (and they are obviously not equal).
I also tried just plugging in f(5) = -2f(5-1)+1 and got -7, but that was not among the answer choices.
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
f%281%29=3
f%285%29=-2f%284%29%2B1
f%284%29=-2f%283%29%2B1
f%283%29=-2f%282%29%2B1
f%282%29=-2f%281%29%2B1=-2%283%29%2B1=-6%2B1=-5
Now work backwards
f%283%29=-2%28-5%29%2B1=10%2B1=11
f%284%29=-2%2811%29%2B1=-22%2B1=-21
f%285%29=-2f%284%29%2B1=42%2B1=43
highlight%28f%285%29=43%29