Multiple choice

If 9! - 2*(7!)² is divisible by 5^n and n is a positive integer, what is the greatest possible value of n?

  1. 1

  2. 2

  3. 3

  4. 4
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A Correct answer
Explanation

9! - 2* (7!)² = (7!) (8*9 - 2*7!) = - 18*(7!) - 18 cannot be divisible by 5. 7! = 1*2*3*4*5*6*7 can only be divisible by 5^1. Since n is a positive integer, so the greatest possible value of n should be 1.

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