During our 12 years in school, we have learned all algebra techniques such as additions, substructions, division and multiplication. In each one of these techniques, there are many techniques. If you have an exam, you know which techniques you need to study to pass the exam. However, in Calculus it is more complicated. In each problem, you need to use a technique before you start solving the problem. In each exam, you will have to use many techniques before you start solving any problem. You are supposed to be able to use each one of these techniques. But there are so many techniques and you don't remember all of them because you haven't used them since long time ago. Or you might be not sure which technique you need to use because some problems can be solved by more than one specific technique. So when students start studying Calculus, the teacher assumes that they already know all the simple techniques that schools teach. Calculus teacher keep repeating this phrases ...