Please answer?

Question

Given below is the odd-number function. Which of the following are equal to O(5)? CHECK ALL THAT APPLY.

O(n) = 2n - 1

A. 5
B. O(4) + 1
C. the fifth odd number
D. 9

Answer 1

If O(n)=2n-1 then O(5)=9

A is wrong
B is wrong as O(4)+1=7+1=8
C is right as 9 is the 5th odd number (or rather the 5th positive odd number)
D is right

so C and D

Answer 2

O(n) = 2n - 1
O(5) = 2(5) - 1 = 9

D) 9 is right.

I might have considered C) as 9 is the fifth odd positive integer. But there is no word 'positive' in the option. So, D) is the only option that suits the question completely.

Answer 3

there is no correct answer, because if you replace n by the given choices, the value from the left side will not equal to the right side.

Answer 4

C and D