AlgebraDifficulty 5.4AIME, harderProve itUnited States
Problem: The number 316990099009901=10132016000000000001 is the product of two distinct prime numbers. Compute the smaller of these two primes.
Solution
Solution: Let x=2000, so the numerator is x5+x4+1=(x2+x+1)(x3−x+1). (This latter factorization can be noted by the fact that plugging in ω or ω2 into x5+x4+1 gives 0.) Then x2+x+1=4002001 divides the numerator. However, it can easily be checked that 101 doesn't divide 4002001 (since, for example, 101∤1−20+0−4), so 4002001 is one of the primes. Then the other one is 10120003−2000+1≈10120003>20002≈4002001 so 4002001 is the smaller of the primes.
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