# Thread: defining a function from irrationals to integers

1. ## defining a function from irrationals to integers

How do I get started on this question?:

Define a function from irrationals to integers by f(a/b) = a - b

(or how the book wrote it) f: Q - Z by f(a/b) = a - b

2. Originally Posted by scottie.mcdonald
How do I get started on this question?:

Define a function from irrationals to integers by f(a/b) = a - b

(or how the book wrote it) f: Q - Z by f(a/b) = a - b
first of all, it is from the RATIONALS to the integers. secondly, there is no question here, you made a statement, you didn't say what to do

3. mmm sorry about that. The full question asks:

Define f: Q - Z by f(a/b) by a - b. Is f a function?

I am wondering what the question is asking, and how/where to start this short problem.

4. Thank you for the help, I was reading the question wrong (oops).

Thanks again for the help

Scott

5. Originally Posted by scottie.mcdonald
mmm sorry about that. The full question asks:

Define f: Q - Z by f(a/b) by a - b. Is f a function?

I am wondering what the question is asking, and how/where to start this short problem.
stop being scared by the math and think about the question as you would any other question of that nature. that's how we start.

lets say i pointed to apple and asked, "is that a dog?" you would respond "no." if i asked "why?" what would you say? well, something along the lines of "well, a dog is a living, breathing thing, it has ears and eyes and fur, etc, since the apple does not have these, it is not a dog."

in other words, to know if something falls under a certain classification, we must know what it means to be in that classification and see if the thing in question fits the bill.

i said all that to say, you need to know what a function is in order to know if something is a function or not. so, what is a function? basically it is a relation where each input value has one and only one output value. is that true in this case? if it is, it's a function, if not, it isn't