The largest value of , for which divides , is
- A
- B
- C
- D
The largest value of , for which divides , is
Correct answer:C
Standard Method
Given: We need the largest value of such that divides .
Find: The maximum integer .
Prime factorize the base:
So,
Now find the powers of and in using Legendre's formula.
Power of in :
Power of in :
For to divide , both of the following must hold:
and
From the first condition,
Therefore the limiting condition is , so the largest possible value is .
The correct option is C.
Minimum Bound Trick
Given: and we want the largest such that divides .
Find: The maximum .
Compare required prime powers directly:
In , the power of is and the power of is .
So,
Hence,
Therefore, the largest value is , so the correct option is C.
Using only the power of and ignoring the power of . Divisibility by requires both prime-power conditions to be satisfied. Always compare all primes appearing in the factorization of .
Factorizing incorrectly. Writing is wrong; the correct factorization is . This changes the condition on the power of .
Taking the larger bound instead of the limiting bound. Since both inequalities must hold together, the correct value of is determined by the minimum permissible bound, not the maximum.
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