Question

Given the following definition, compute Q(5).
Q(n) =

0 if n = 0
1 if n = 1
3 if n = 2
Q(n − 1) + Q(n − 2) + Q(n − 3) if n > 2

Answer 1

Q(0) = 0
Q(1) = 1
Q(2) = 2
Q(3) = Q(2) + Q(1) + Q(0) = 2 + 1 + 0 = 3
Q(4) = Q(3) + Q(2) + ...............
Get the idea?

Answer 2

You have to calculate all the Q() s up through Q(4) in order to calculate Q(5).
I've already done most of it for you.

Answer 3

how did you get q(0)?

Answer 4

Right from your question.
You wrote: Q(n) = 0 if n=0
That means Q(0) = 0