Respuesta :
f4 can be rewritten to:
f(4) = f(3+1) = -2f(3) [Using f(n+1) = -2f(n)]
Keep using f(n+1):
-2f(3) = -2f(2+1) = -2[-2f(2)] = 4f(2)
Again:
4f(2) = 4f(1+1) = 4[-2f(1)] = -8f(1) = -8*160
-8*160 = -1280
f(4) = f(3+1) = -2f(3) [Using f(n+1) = -2f(n)]
Keep using f(n+1):
-2f(3) = -2f(2+1) = -2[-2f(2)] = 4f(2)
Again:
4f(2) = 4f(1+1) = 4[-2f(1)] = -8f(1) = -8*160
-8*160 = -1280