Which of the following sets represents a function?

{(1,1), (2,1), (3,1), (4,1)}

{(1,1), (1,2), (1,3), (1,4)}

{(1,1), (2,1), (2,2), ( 3,1)}

{(2,1), (2,2), (3,2), (4,2)}

Question

Which of the following sets represents a function? 

 {(1,1), (2,1), (3,1), (4,1)} 

 {(1,1), (1,2), (1,3), (1,4)} 

 {(1,1), (2,1), (2,2), ( 3,1)} 

 {(2,1), (2,2), (3,2), (4,2)}

larseighner · Answer

In a function, any x can only be associated with one unique y.

jdoe0001 · Answer

a function will have no X-REPEATS
so let's check the last  set then  for any x-repeats   $\large \begin{array}{llll}
\{(&{\color{brown}{ 2}},1), (&{\color{brown}{ 2}},2), (3,2), (4,2)\}\
 &\uparrow &\uparrow \
&{\color{brown}{ repeat}}&{\color{brown}{ repeat}}

\end{array}$  so that one is NOT a function, because it has x-repeats
so try the others