To determine if there exists an integer n such that n2+n+1 is divisible by 1955, we need to check the divisibility of n2+n+1 by the prime factors of 1955.
First, factorize 1955:
1955=5×17×23
We need to check if n2+n+1 can be divisible by each of these prime factors.
1. Check divisibility by 5:
n2+n+1≡0(mod5)
We need to check the possible values of n modulo 5:
nnnnn≡0(mod5)⟹n2+n+1≡02+0+1≡1(mod5)≡1(mod5)⟹n2+n+1≡12+1+1≡3(mod5)≡2(mod5)⟹n2+n+1≡22+2+1≡7≡2(mod5)≡3(mod5)⟹n2+n+1≡32+3+1≡13≡3(mod5)≡4(mod5)⟹n2+n+1≡42+4+1≡21≡1(mod5)
None of these results are congruent to 0 modulo 5. Therefore, n2+n+1 is never divisible by 5.
Since n2+n+1 is not divisible by 5, it cannot be divisible by 1955 because 5 is a factor of 1955.
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