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Asked by nishant27_c | 15th Jan, 2010, 03:07: PM

Expert Answer:

To prove n , n+2 or n+4 is divisible by 3,

Case 1 Let n is divisible by 3

So n = 3k for some positive integer k

Now n+2 = 3k+2 which is not divisible by 3

n+4 = 3k +3+1 =3(k+1)+1 =3m+1 not divisible by 3

Case 2 n+2 is divisible by 3  so

n+2 =3k

so n =3k-2  not divisible by  3

n+4 = 3k+2 = not divisible by  3

Case 3: Let n+4 is divisible by 3 so n+4 = 3k

n =3k-4=3(k-1)-1=3m-1 not divisible by 3

n+2 = 3k-2 not divisible by 3

 

Answered by  | 15th Jan, 2010, 03:19: PM

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