Sunday, 20 December 2015

functions - Proving: f is injective Leftrightarrowf(XcapY)=f(X)capf(Y)








Let A := "f is injective" and B := "f(XY)=f(X)f(Y)".



My first idea is to show BA through contraposition, so ¬A¬B. Would it then be enough if I say: f is not injective and then show an example where the equation in B is wrong? Would it be a proof then?

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