SOLUTION : Let a be any odd positive integer and b = 7 By division Lemma there exists integers q and r such that
⇒ a = 7q or , a =7q+1 or , a =7q + 2 or, a=7q+3 or, a=7q+4 or, a =7q+5 or , a =7q +6 ⇒( r = 0,1,2 ,3 ,4 ,5 ,6 )
⇒ Hence, any odd integer is of the form 7q+1 ,7q+2 ,7q+3 , 7q+4 ,7q+5 ,7q+6
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