Define Function

• Aug 31st 2009, 06:09 AM
sharkman
Define Function
Tell me, why is x = |y| NOT a function?

Also, would y = |x| be a function? If so, why?
• Aug 31st 2009, 06:17 AM
e^(i*pi)
Quote:

Originally Posted by sharkman
Tell me, why is x = |y| NOT a function?

Also, would y = |x| be a function? If so, why?

A function is where a value of x corresponds to exactly one value of y.

With this equation it is clear that f(-4) = f(4) and so is not a function
• Aug 31st 2009, 07:44 AM
sharkman
So...
Quote:

Originally Posted by e^(i*pi)
A function is where a value of x corresponds to exactly one value of y.

With this equation it is clear that f(-4) = f(4) and so is not a function

So, x = |y| means that y varies in terms of values and thus making this equation NOT a function, right?

Is that what makes it different from y = |x|?
• Aug 31st 2009, 08:34 AM
Matt Westwood
Because you can plug in any value of x and you can be guaranteed to get exactly one value of y out the other end. That's what defines a function: every value of x has exactly one value of y.
• Aug 31st 2009, 08:08 PM
sharkman
ok...
Quote:

Originally Posted by Matt Westwood
Because you can plug in any value of x and you can be guaranteed to get exactly one value of y out the other end. That's what defines a function: every value of x has exactly one value of y.

Easily explained.