determining functions

[kangsang24]

I am relearning algebra on my own and I am just starting the chapter on functions.
It is defined as having only one "y" value for every "x" value.
The book gives an example of a function:
y=(4-x^2)/-2

why is this a function?!?!

for example, if "x" was 1 or -1, "y" would be -3/2

 

[lookagain]

I am relearning algebra on my own and I am just starting the chapter on functions.
It is defined as having only one "y" value for every "x" value. \(\displaystyle \ \ \ \ \) <-----------
The book gives an example of a function:
y=(4-x^2)/-2

why is this a function?!?! \(\displaystyle \ \ \ \ \) Is it not satisfied by the statement above?

for example, if "x" was 1 or -1, "y" would be -3/2

.

 

[stapel]

...functions.
It is defined as having only one "y" value for every "x" value.

Yes. For any x-value, there will be only one y-value. However, two different x-values may lead to the same y-value.

 

[HallsofIvy]

Your difficulty appears to be confusing "x" (the idependent variable value) with "y" (the function value). For any given value of x this formula gives a single possible value of y. For a function a single value of x cannot give two different values of y. The fact that two different values of x give the same value of y means it is not a one to one function but it is still a function.