Explanation:
0 steps to reach floor 0.
a.
floor 0 to floor 1 = floor 0 + 14 = 0 + 14 = 14
floor 1 to floor 2 = floor 1 + 14 = 14 + 14 = 28
floor 2 to floor 3 = floor 2 + 14 = 28 + 14 = 42
floor 3 to floor 4 = floor 3 + 14 = 42 + 14 = 56
floor 4 to floor 5 = floor 4 + 14 = 56 + 14 = 70
b.
when we look at the calculation for the stairs to floor 1, then we see
floor 1 = floor 0 + 14 = 0 + 14 = 14
and for floor 2
floor 2 = floor 1 + 14 = floor 0 + 14 + 14 = 0 + 14 + 14 = 28
and for floor 3
floor 3 = floor 2 + 14 = floor 0 + 14 + 14 + 14 = 42
and so on.
we see
floor n = s(n) = s(0) + 14×n = 0 + 14×n = 14n
s(n) = 14n