第一題:
Let A ={1,2,3,4}and B={a,b,c,d,e}.Let f:A→B be defined by f={(1,d),(2,e),(3,d),(4,b)} and g:B→A {(a,2),(b,1),(c,3),(d,1),(e,4)}.List the ordered paris in f。g and g。f .
第二題:
Let R be the relation on Z*N defined by (a,b) R (c,d) if ad=bc,then prove that R is an equivalence relation.
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