Order pairs question

Question

 

In which set of ordered pairs is y a function of x?

 

 

a. (-1, 2) (0, 1) (0,2) (1,1)            b. (-4, 1) (-3, 1) (-2, 1) (-1, 1)

c. (1, -4) (1, -3) (1, -2) (1, -1)       d.(2, 5) (3, 6) (6, 5) (2, 7)

Answer 1

In order for y to be a function, it must pass the vertical line test.  This means that if the function crosses the vertical line only once, then y is a function.

 

The function must not have points in which the x-coordinate repeat.  For example,  if the function has points (2,5) and (2,9), this is NOT a function.

 

The only answer choice whose order pairs  define a function is (b).