please help with functions

Question

anonymous · Answer

It's a function..

isaiah.feynman · Answer

The graph is a function because it obeys the vertical line test.

anonymous · Answer

In every one value of x, there is exactly one value of y.

isaiah.feynman · Answer

@liliegirl I think you are talking of the horizontal line test.

anonymous · Answer

In mathematics, a function is a relation between a set of inputs and a set of permissible outputs with the property that each input is related to exactly ONE output.

mathmale · Answer

Hey, trollface, I agree with you that the "vertical line test' applies here, and that for each x value you'll associate exactly one y value.  So:  does the given graph represent a function or not/

mathmale · Answer

cOOL.

mathmale · Answer

Could you, trolley, explain what the horiz. line test is for?

anonymous · Answer

@Isaiah.Feynman 
Horizontal line test is used to determine if the function is injective.
right?

mathmale · Answer

You may not have been exposed to this "test" before.  Sometimes we have to decide whether a given function as an inverse.  If a horiz. line drawn thru the graph of the given fn. hits it in only one place, then the function does have an inverse.  If two or more places, the given fn. doesn't have an inverse.  Just for ref.

isaiah.feynman · Answer

@trollface that definition is for the horizontal line test. Not the vertical line test. The vertical line test, tests to see if the graph of some equation is a function. If the vertical line intersects the graph once then the equation is a function. If it intersects the graph more than once then the equation is not a function. The horizontal line test, tests to know if a function is one to one. A one to one function has only one y value for every x value. Graphically if a horizontal line intersects the graph of a function once then the function is one to one. If it intersects the graph more than once then the function is not one to one.

mathmale · Answer

Thanks for pointing this out, Isaiah.  I'd substitute "inversible" for "injective."  But I think we're on the same wavelength.  :)

anonymous · Answer

Thank you @mathmale i'll definitely note that down for future reference.

mathmale · Answer

IF.  I believe trollface already knew that, judging by his responses earlier.  But thanks for the very nice summary, which is quite accurate.

anonymous · Answer

Aah, I understand now, I was getting it a little mixed up, thanks for the thorough explanation. @Isaiah.Feynman

mathmale · Answer

for he's a jolly good fellow, which nobody can deny!

mathmale · Answer

:)    over and out.

anonymous · Answer

agreed :) @mathmale thanks again!

mathmale · Answer

Bye!