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Define * on N by m * n = 1 cm (m, n). Show that * is a binary operation which is commutative as well as associative. |
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Answer» * is an operation as m*n = LCM (m, n) where m, n ∈ N. Let m = 2 and b = 3 two natural numbers. m*n = 2*3 = LCM (2, 3) = 6∈ N So, * is a binary operation from N x N → N. For commutative, n*m = 3*2 = LCM (3, 2) = 6∈ N Since m*n = n*m, hence * is commutative operation. Again, for associative, let p = 4 m*(n*p) = 2*LCM (3, 4) = 2*12 = LCM (2, 12) = 12∈ N (m*n) *p = LCM (2, 3) *4 = 6*4 = LCM (6, 4) = 12∈ N As m*(n*p) = (m*n) *p, hence * an associative operation. |
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