Unsure if this is the right section but here goes:

By coordinte geometry, any line or circle is of the form Ax+By+C( ) = D, where A, B, C, D are real constants.

Set = u + iv.

Show that u = and v = .

Deduce that the linear fractional transformation sends a line or a circle to another such.

I'm really quite stumped by this...I don't see where the 1/z comes into all this...and just in general don't know how to start with this?

Any hints or help would be greatly appreciated.