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The operation is defined by x y = 1/x + 1/y for all nonzero [#permalink]
15 Nov 2008, 14:08
The operation Θ is defined by x Θ y = 1/x + 1/y for all nonzero numbers x and y. If z is a number greater than 1, which of the following must be true? I. x Θ (-z) = 0 II. z Θ z/(z-1)= 1 III.2/z Θ 2/z= z A. I only B. I and II only C. I and III only D. II and III only E. I, II, and III