(x,y)
domain is input or x
range is output or y
(x,y)
(-1,5)
(0,6)
(-1,7)
(2,9)
the domain is D={-1,0,2}
range is R={5,6,7,9}
it isi a function if no x repeats with a differnt y
we see that we have (-1,5) and (-1,7)
-1 repeats with 5 and 7
it is not a function
