# tetori

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bio website tetori.blog.me location South Korea age 19 member for 1 year, 11 months seen 5 hours ago profile views 1,592

I am not good at English, so any correction of grammatical error would be welcomed.

 66 which is larger number? $\sqrt{7}-\sqrt{6}$ or $\sqrt{6}-\sqrt{5}$ 30 The series $\sum_{n=1}^{+\infty}\frac{1}{1^2+2^2+\cdots+n^2}.$ 28 Does $\bigcap_{n=1}^{+\infty}(-\frac{1}{n},\frac{1}{n}) = \varnothing$? 18 Does the sequence $1,-1,1,1,-1,1,1,1,-1,1,1,1,1,-1,1,1,1,1,1,-1,\ldots$ have a closed form? 14 An inequality $\,\, (1+1/n)^n<3-1/n \,$using mathematical induction

# 10,090 Reputation

 +10 Product of $n$ consecutive positive integer is not a $n$th power? +10 Hereditary cardinality and products of sets +10 Set theory and logic proof +10 If $G$ is abelian, prove that $H = \{g \in G \mid g^2 = e\}$ is a subgroup of $G$.

# 34 Questions

 13 Can we prove the existence of $A\cup B$ without the union axiom? 12 If polynomial with rational number is injective on rationals then it is injective on reals? 9 The cardinality of the set of all linear order types over $\omega$ is $2^{\aleph_0}+\aleph_1$ in ZF+AD? 8 Integration of $\sqrt{x+\sqrt{x^2+3x}}$ 7 There is a second-order sentence that is valid in standard semantics but not valid in Henkin semantics?

# 115 Tags

 149 real-analysis × 57 52 elementary-number-theory × 13 115 calculus × 35 50 abstract-algebra × 19 105 sequences-and-series × 24 48 elementary-set-theory × 30 66 arithmetic 48 analysis × 15 60 general-topology × 33 39 integration × 14

# 6 Accounts

 Mathematics 10,090 rep 41359 Area 51 156 rep 3 TeX - LaTeX 101 rep 2 Theoretical Computer Science 101 rep 3 Computer Science 101 rep 2