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Let * be a binary operation on N given by a * b = 1 cm of a and b. Find the value of 20 * 16. Is * (i) commutative, (ii) associative? |
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Answer» We know that a * b = LCM of a and b So 20 * 16 = LCM of 20 and 16 = 80 Commutative: Consider a and b ∈ N So LCM of a and b = LCM of b and a Here, a * b = b * a Ɐ a and b ∈ N Therefore, * is commutative. Associative: (a * b) * c = LCM of a and b * c Here, = LCM of {(LCM of a and b) and C} = LCM of {LCM of a, b and c} We get = LCM of (a and [LCM of b and c]) = a * (LCM of b and c) So = a * (b * c) We can write it as a * (b * c) = (a * b) * c Ɐ a, b ∈ c ∈ N. Therefore, * is associative. |
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