Which set of ordered pairs represents a function?

Question

{(1,3),(−7,−1),(8,−8),(1,−9)}{(1,3),(−7,−1),(8,−8),(1,−9)}

{(−1,−1),(−9,−1),(−8,0),(−4,−4)}{(−1,−1),(−9,−1),(−8,0),(−4,−4)}

{(6,−5),(−5,3),(−5,−8),(−2,7)}{(6,−5),(−5,3),(−5,−8),(−2,7)}

{(−3,5),(−3,−3),(7,−7),(0,5)}{(−3,5),(−3,−3),(7,−7),(0,5)}

Answer 1

no

yes

no

no

only the 2nd is a function

the others have points where there is more than one y value for a given x value

if you plot the points, if it fails the vertical line test, it's not a function

1st, 3rd and 4th sets of points fail the vertical line test

if you can draw a vertical line and it intersects more than one point, it fails the vertical line test