Math Help - function question

1. function question

Let R be the set of real numbers.let A=R - {-1/2} and B=R - {2}.let f be a function from A to B defined by f(x)= 4x-3 / 2x+1.

i) Show that f is 1-1
ii) show that f is onto
iii) does f have an inverse? if so find the inverse?

i)f(a)= 4a-3 / 2a+1

f(b) = 4b-3 / 2b+1

4a-3 / 2a+1 = 4b-3 / 2b+1
4a-3(2b+1) = 4b-3(2a+1)
8ab-6b+4a-3 = 8ab-6a+4b-3
-6b = -6a
a=b
hence 1-1

Im having trouble with the onto and inverse part. Can someone assist me please?

2. Re: function question

To get the inverse let f(x)=y
$y= \frac{4x-3}{2x+1}$

Rearrange this to get x in terms of y
Then change the variables so that x becomes f(x) and y becomes x

3. Re: function question

For a function to be invert-able it must be 1-1 and onto .I got that part but how do i do the inverse?

4. Re: function question

I just explained how to get the inverse. Try it and if it doesn't work then show us what you tried

5. Re: function question

Originally Posted by Shakarri
I just explained how to get the inverse. Try it and if it doesn't work then show us what you tried
x= y-3 / 2y - 4

f(x) = x-3 / 2x - 4

is this it?