Proof need helps

[Vance]

I have

x_n_+_1=x_n - \frac{f(x_n)}{g(x_n)}

where

g(x)=\frac{f(x+f(x))-f(x)}{f(x)}

and i am asked to prove that this is quadratically convergent under suitable hypotheses...

Can you help me ?

Thanks in advance,

[Vance]

I proved for you, can you prove me back ?

Thanks