数分问题求证明

数分问题求证明
Exercise 8.Suppose on a recent exam,Amy received an A,Joe received a D,Meg
received a B,and Sam received an A.
Let R = { Amy,Joe,Meg,Sam }10 1.PREPARATORY MATERIAL
Let S = {A,B,C,D,F}
Let T = {A,B,D}
Let f = {(Amy,A),(Joe,D),(Meg,B),(Sam,A)}
Let g = {(A,Amy),(D,Joe),(B,Meg),(A,Sam) }
Let h = {(A,Amy),(D,Joe),(B,Meg) }
Use the definition of a function to explain why the following statements are true:
• f is a function from R to T.
• f is not a function from T to R.
• f is a function from R to S.
• g is not a function from T to R.
• h is a function from T to R.
• h is not a function from S to R.