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show that the cube of any positive imtegerte or the form am amt) or ama 8 for someinteres m |
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Answer» Let a be any positive integer and b = 3 a = 3q + r, where q ≥ 0 and 0 ≤ r < 3 ∴ r = 0,1,2 . Therefore, every number can be represented as these three forms. There are three cases. Case 1: When a = 3q, Where m is an integer such that m = Case 2: When a = 3q + 1, a = (3q +1) ³ a = 27q ³+ 27q ² + 9q + 1 a = 9(3q ³ + 3q ² + q) + 1 a = 9m + 1 [ Where m = 3q³ + 3q² + q ) . Case 3: When a = 3q + 2, a = (3q +2) ³ a = 27q³ + 54q² + 36q + 8 a = 9(3q³ + 6q² + 4q) + 8 a = 9m + 8 Where m is an integer such that m = (3q³ + 6q² + 4q) Therefore, the cube of any positive integer is of the form 9m, 9m + 1, or 9m + 8. Hence, it is proved . |
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