I need help with this math problem... Its pretty easy?

Question

Yes i know its easy, but i forgot what a function was. Here it is

Determine if each relation is a function:

1.

[ (0,0), (1,-1), (2,7), (1,5) ]

Question 2.

[ (3,2), (4,3), (5,2), (6,1) ]

Please help me with this, and thank you for your answers.

Answer 1

All you do is see if all the x coordinates are different.  If yes, it is a function; if no, it isn't.  So here, 1 isn't (two points have x = 1) but 2 is.

Answer 2

1 george washington

2 mars

Answer 3

1. no

2. yes

All you have to do is see if each x value only has one y value associated with it. In question one, the x value of one has two y values, so its not a function. In question two, each x only has one y value, so it is a function.  

Answer 4

1 is not a function and 2 is a function