Question

Given below is the odd-number function. Which of the following are equal to O(20)? Check all that apply. O(n) = 2n - 1 A. O(19) + 1 B. The twentieth odd number C. 39 D. 19

Answer 1

The answer 
the only method for finding the answer is computing directly the value of O(20) by replacing n by  20, 
since we know that O(n) = 2n - 1
so, we get O(20) = 2*20 - 1 = 40-1=39
the answer is D. 19