Assume that f : R^n → R^n is continuously differentiable, and that there is
a positive number c such that
|| f(x) - f(y) ||≧ c || x-y || for all x,y in R^n.
(a) Prove that f(R^n) is open.
(b) Prove that f(R^n) is close.
(c) What can you conclude from (b) and (c)
攤手了…..╮(﹋﹏﹌)╭..
和今年台大考題好像…可惜分數也飛了！
請教大師
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