Question

In exercise 33, which sets of ordered pairs represent functions from A to B.
33. A= {10,20,30,40} and B={0,2,4,6}
(a) {(20,4),(40,0),(20,6),(30,2)}
(b){(10,4),(20,4),(30,4)(40,4)}
(c){(40,0),(30,2),(20,4)(10,6)}
(d){(20,2),(10,0),(40,4)}

Answer 1

when you have a function from A to B, you basically have a set of ordered pairs

each ordered pair is of the form (x,y) where x is drawn from set A and y is drawn from set B

Answer 2

keep in mind that for it to be a function, each x must map to exactly one y

Answer 3

as jim_thompson5910 said from the sets at a,b,c,d the set that doesn't have a X-REPEATS
that is

the set whose first value doesn't repeat

let's take a close look at the 1st set made by A and B, the set "a" \(\large \begin{array}{llll}
(a) \qquad \{(&{\color{brown}{ 20}},4),({\color{brown}{ 40}},0),(&{\color{brown}{ 20}},6),({\color{brown}{ 30}},2)\}\\
&\uparrow &\uparrow \\
&repeat&repeat

\end{array}\) so set "a" has a first value that's repeated, thus is NOT a function
check the others