What are the differences between the different international payments? I seem to be missing some notes on it =/.
Also, can someone explain derivatives, I have no idea what it is.
What is the discriminant used for and how do you know which types of questions requires the use of the discriminant.
For example, the last question 16c in the 2012 paper requires you to use the discriminant, but i don't understand why. Help would be much appreciated thanks and best of luck...