Question 911180
Assume {{{n}}} is even.
{{{n^2}}} is even (even number of times adding an even number)
{{{3*n}}} is even
So then,
even - even + odd = even + odd = odd
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Assume {{{n}}} is odd.
{{{n^2}}} is odd (odd number of times adding an odd number)
{{{3*n}}} is odd
odd - odd + odd = even + odd = odd
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True.