For x positive integers, function f(x) which remains a mystery and nobody knows can be divided by all of the following five EXCEPT one number. 1, 2, 3, 4 and 6. Can you figure out which number cannot divide f(x)?
The answer is:
Any function can be divided by 1. So, we eliminate 1. Next, if the function couldn't be divided by 2, then, it also would not be divisible by 4 or 6 which violates our condition. This, 2 is eliminated. Next, by similar logic, 3 is also eliminated. This, we know for sure that f (x) is divisible by 1,2 and 3. As, it is divisible by both 2 and 3, it would be divisible by 6 too. Thus, the only remaining number by which it is NOT divisible is 4.