For the function f:R -->R which is

f(x): -1 when x<0

1 when x>0

0 when x=0

prove that there is no limit at x=0. I'm told I can use a proof by contradiction.

What do you guys think? I've seen I can do something with derivatives or something, but I haven't been taught that yet. I just learned delta-epsilon proofs. (I looked at the sticky, but it wasn't helpful to me).

Thanks!

Regards,

Esther