hellppppppppppp

Thanks Chris,

Alan keeps telling me I have to rearrange the equation to make x the subject BEFORE I can swap the x and the y.  (just as Chris has told you here)

I have never understood what difference it makes. Especially not if graphing 'holes' are pre-recognised :) Mmm

Let's write this as 

y =(1/4)x + 3

Here's the strategy

1. Get x by itself

2. "Swap" x and y

3. For "y" write f^-1(x)

So

y =(1/4)x + 3    add 3 to both sides

y - 3 =(1/4) x     multiply both sides by 4

4y - 12  = x      we have x by itself

Now, "swap" x and y

4x - 12 = y

For "y" ..... write f^-1(x)

f^-1(x)  = 4x - 12  ...and we can write this as 

f^-1(x) = 4(x - 3)