Question 1136860
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Your post seems strange to me, and I'd like to discuss it with you.



This fragment  " d |2 ", in standard context (in standard designations), means that " d divides 2 ",  

or (which is the same),  " d is divisor of 2 ".



Then, since we consider only natural numbers in this assignment, it implies  d = 2.



Then the first line  (the "given" part) means that  n+1  and (n^2+1) both are even numbers.



But it contradicts to what has to be proved.
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So, in my view, the post is DEFECTIVE and must be edited.