Recent content by helpmeppl

for the proof that it's only differentiable at 0, can proving that the function is not continuous everywhere except zero sufficient?

that proves that the function is differentiable when x=0, but how can i prove that that's the only x that satisfies f's differentiability. thanks.

1. function is x^2 if x is rational 0 if x is irrational. I need to prove that function is only differentiable at 0. 2. f'(x)=lim(h->0)=(f(x+h)-f(x))/h 3. fruitless attempt-----> So f'(0)=lim(h->0) f(h)/h=lim(h->0)x since it's 0 when irrational and x when rational, 0 when irrational, x=0...