For the memoized part, to compute term, we need additions. Thus it is linear in time complexity.
Without memoization, to compute term, the
add-streams take two fib streams(
(cdr fib)) and add their first term. Or we add . Now the problem is that unlike in the memoized part this sums are recomputed again! So in a way we are back to our resursive version of fibs that we saw here. There are already saw that this is a exponential time complexity.