fn= fn – 1, if n is odd= 2fn-1, if n is even.If f0 = 1, then find the value of f20 + f21.
Soln:
Option (b)
f4 + f5 = 2f3 + f4 = 2f2 + 2f3 = 4f1 + 2f2 = 4f0 + 4f1 = 4f0 + 4f0 = 8f0 = 8
Hence option (e)
OR starting with
f(0) = 1
F(1) = 1
F(2) = 2
F( 3) = 2
F(4) = 4
F (5) = 4
F(6) = 8
F(7) = 8
……………..
…………….
F(N) =2N/2
F(N+1) = 2N/2
Therefore f( 20) = 210and f(21) = 210
f(20) + f(21) =1024+1024 = 2048