
Bobosharif S. answered 04/17/18
Tutor
4.4
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Mathematics/Statistics Tutor
For n=1, we have 1-1=0, 0 is divisible by 3.
Assume that this is true for n and we have to show that its true for n+1
(n+1)3-(n+1)=n3+3n2+2n=n3-n+3(n2+n) is divisible by 3; n3-n by 3 by is divisible by assumption and 3(n2+n) is divisible as well. So, if n3-n is divisible by 3, then (n+1)3-(n+1) is divisible as well.