at x = -2

what you want to show is the following:

for , there exists such that:

for all x that belongs to dom f\{c} s.t.

i remember working backward in problem like these. Start out with something like this...

let ,

for

... (you'll prolly need to use some algebraic formula for cube/cluberoots and perhaps triangle inequality as well

...

...

P.S. I'll try this later on.