This is a follow-up question of this one:
Proof of the square root inequality 2√n+1−2√n<1√n<2√n−2√n−1
I am interested in the following generalizations of the square root inequality.
Let ε,δ>0. Then
√ε+δ−√ε<δ2√ε.
If additionally δ<ε, then
δ2√ε<√ε−√ε−δ.
The proof is similar as answered in my previous question.
Moreover, if ε,δ∈C are any complex numbers and √⋅ is a complex root, then
min(|√ε+δ−√ε|,|√ε+δ+√ε|)≤min(|δ|√|ε|,√|δ|).
I have trouble to prove this one, but it should hold (it is not from me). What I have yet is the following: first suppose
|√ε+δ−√ε|≤|√ε+δ+√ε|.
Then
|√ε+δ−√ε|2≤|δ|,
so that
|√ε+δ−√ε|≤√|δ|.
Similarly, when
|√ε+δ−√ε|≥|√ε+δ+√ε|,
then
|√ε+δ+√ε|≤√|δ|,
so that
min(|√ε+δ−√ε|,|√ε+δ+√ε|)≤√|δ|.
Moreover,
|√ε+δ−√ε|=|δ||√ε+δ+√ε|≤…
and I don't know how to continue. Any help for solving this?
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