A Note On Primitive Roots

In the first chapter of this paper,we introduce the congruences,Euler phi function,Lagrange's theorem,primitive roots and so on.In the second one,we deal with an equation about Euler phi function and the existence of primitive roots of modulo p.In the third one, we give a direct proof of the existence of primitive roots of modulo p~l(p is an odd prime, and l≥1).In the fourth one,we compare two methods of the existence of primitive roots of modulo p~l.