Which of the following sets of ordered pairs is a function?

Question

A.
(5,10), (-8,2), (-1,7), (-5,10)

B.
(5,10), (-8,2), (-1,7), (-1,-5)

C.
(10,5), (2,-8), (7,-1), (10,-5)******

D.
(-1,10), (-8,2), (-1,7), (-8,-5)

am I right?

Answer 1

No. How can f(10) be both 5 and -5?
look for a relation where each x-value is used only once.