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 Question from Parag, a student: if n is a natural number,then 3n^5+7n is divisible by a)2 b)3 c)5 d)7 i got the answer but still i need a valid alternate approach.

Hi,

You have four options for the correct answer. I would begin with some experimentation.

If $n = 1$ which of the options are valid? Any others you can rule out.

If $n = 2$ which of the options are valid? Any others you can rule out.

At this point you have only one possibility for the correct answer. Can you prove this option is valid? I used properties of even and odd integers.

Penny

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