In order to get Figure II, Figure I has only been moved.
It hasn't been rotated or reflected, or any of that weird stuff.
In order to move any vertex from its position in Fig-I
to its position in Fig-II, you have to move it 2 units left
and 4 units up. That will take any point from Fig-I and
put it right where it belongs in Fig-II.
Well OK. If you have a point with the coordinates (A, B), then
-- What do you need to do to 'A' to move the point 2 units left ?
You need to subtract 2 from A .
-- What do you need to do to 'B' to move the point 4 units up ?
You need to add 4 to B .
So, in order to take Fig-I and move it 2 units left and 4 units up,
to where it can lay right on top of Fig-II,
every 'x' has to become x - 2
and every 'y' has to become y + 4 .
