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tmua.me Medium Set B Paper 2 · Q5

Paper 2Logic & proofNumber & counting

Consider the following claim about positive integers mm and nn:

If m+nm+n is prime, then mn+1mn+1 is prime.

Which of the following is a counterexample to this claim?

Am=2,n=3m=2,\quad n=3
Bm=4,n=8m=4,\quad n=8
Cm=1,n=6m=1,\quad n=6
Dm=3,n=8m=3,\quad n=8
Em=2,n=7m=2,\quad n=7

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