I'm just stuck on this problem :
We want to solve f(x)=0 via a function of iteration x=g(x) that satisfies the necessaries conditions of convergence. Determine a bound of the error which is committed in each step in function of the difference between the 2 last values of the sequence. In other words, determine C such that |x_{n+1}-x_*|\leq C |x_{n+1}-x_n|. Where x_* is the zero that we are looking for.
Tip : Use the triangular inequality in the inverse sens than usual.
I don't know how to start. I'm stuck at starting it and I need it to solve the second part of the exercise.