Assume the function f(x, y) is continuous on R2 and that for point (a, b) in R2, we have f(a, b) > 0.
Prove that there exists a real number r > 0 such that for all x, y, |x−a| < r,&|y−b| < r ==> f(x, y) > 0.
(this is relevant to the beginning of the proof of IFT.)
Attempt:
So we know...