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Nov
8
comment Change of variables problem.
The image seems to be not related to the question. Is it?
Nov
8
answered Help with summation: $\sum_{k=1}^\infty\frac{k(k+2)}{15^k}$
Nov
8
comment Non-uniqueness of solutions of an ordinary differential equation
This is a gap in many courses. I have seen books which write that the solution to $x'=2\sqrt x, x(0)=0$ is $x=t^2$. Which is not only inaccurate but completely wrong for $t<0$.
Nov
8
revised Non-uniqueness of solutions of an ordinary differential equation
deleted 1 character in body
Nov
8
answered What is the limit of $\frac{a + (n-1)d}{2a + 2(n-1)d}$ for $n \to \infty$?
Nov
8
answered Non-uniqueness of solutions of an ordinary differential equation
Nov
7
comment Prove that $F_n < 2^n$ for every $n \geq 0$ - Mathematical induction
Proving $P(n)\Rightarrow P(n+1)$ for all $n\ge 1$ is the same as proving $P(n-1)\Rightarrow P(n)$ for all $n\ge 2$.
Nov
7
answered Notation for a set $\{a_1,a_2,a_3,a_4\}$, $a_i \in \{0,1\}$ for $i = 1,2,3,4$?
Nov
7
comment Prove that $F_n < 2^n$ for every $n \geq 0$ - Mathematical induction
what you have written is correct. You have proved that $F_n < 2^n$ for $n\ge 2$. Why do you feel that the usual definition is something different?
Nov
6
revised Applications of the formula expressing roots of a general cubic polynomial
deleted 3 characters in body
Nov
6
asked Applications of the formula expressing roots of a general cubic polynomial
Nov
3
comment Prove the function $f(x) = (a*x)^{-1}$ is bijective
Taking the inverse of both sides you get: $a*x = a*y$... This is elementary algebra, like when you want to simplify the equation $1/(7x) = 1/(7y)$.
Nov
2
revised Representation of an Abelian Lie algebra
english
Oct
30
comment Prove the function $f(x) = (a*x)^{-1}$ is bijective
The inverse of $(a*x)^{-1}$ is $a*x$.
Oct
30
answered Prove the function $f(x) = (a*x)^{-1}$ is bijective
Oct
30
comment Proving a subset of a metric space is bounded
You should mention what is the definition of bounded, since what you are asked to prove could be a definition.
Oct
26
comment The mathematics underlying Rubik's games
See math.harvard.edu/~jjchen/docs/…
Oct
26
revised Help with proving property of Rubik's cube.
added 67 characters in body
Oct
26
answered Help with proving property of Rubik's cube.
Oct
26
comment Sobolev embedding theorem, inequalities
Maybe you can take $p=+\infty$ if $n<3$...