SOLUTION: How do you test if something is a function on a graph? ......I remember my teacher saying something about using a pencil and lying it down on the graph, or something like that...pl

Question 42161: How do you test if something is a function on a graph? ......I remember my teacher saying something about using a pencil and lying it down on the graph, or something like that...please help!!!-I have a final TOMMMORROW!!!
Answer by fractalier(6550) (Show Source): You can put this solution on YOUR website!
You do the "vertical line test."
And yes, you can use your pencil.
Lay your pencil straight up and down on the paper on the graph of the "function."
If your pencil crosses the "function" MORE THAN ONCE, it is NOT a function, but only a relation.
The idea for a function is, that for any x you choose, ONLY ONE y exists.
Good luck on the final.
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