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seen Aug 19 at 6:23

Apr
5
comment if $abc=1$, then $a^2+b^2+c^2\ge a+b+c$
But what if $a<0$?
Apr
5
comment if $abc=1$, then $a^2+b^2+c^2\ge a+b+c$
A spoiler is generated by starting your line with >!
Apr
5
reviewed Approve suggested edit on Find $t$ in $N = b \times g^t$.
Apr
5
answered Is there a way to denote the calculation $1+2+3+\dots+n$?
Apr
5
comment String transformation
@Henry: If I understand the rules correctly: $\mathbf{BB}BGRGBBB$ $\to$ $\color{red}{B}\mathbf{\color{red}{B}B}GRGBBB$ $\to$ $B\color{red}{B}\mathbf{\color{red}{B}G}RGBBB$ $\to$ $BB\color{red}{R}\mathbf{\color{red}{R}R}GBBB$ $\to$ $BBR\color{red}{R}\mathbf{\color{red}{R}G}BBB$ $\to$ $BBRR\color{red}{B}\mathbf{\color{red}{B}B}BB$ $\to$ $BBRRB\color{red}{B}\mathbf{\color{red}{B}B}B$ $\to$ $BBRRBB\color{red}{B}\mathbf{\color{red}{B}B}$ $\to$ $\mathbf{B}BRRBBB\color{red}{B\mathbf{B}}$ $\to$ $\color{red}{B}BRRBBBB\color{red}{B}$.
Apr
3
comment is there an efficient algorithm for comparing collections of points?
Calculating the distances between pairs of points $p_i$ is $O(M^2N)$ (because there are $M(M-1)/2$ point pairs, and calculating the distance means $N$ squares, $N-1$ additions and a single square root). The same is true for the points $q_i$. That way you've reduced the problem to comparing graphs with weighed edges for equivalence; however I don't know if there is a polynomial algorithm for that.
Apr
3
comment Visually stunning math concepts which are easy to explain
Well, I looked at that picture and thought: "Err ... how does this work?" I figured it out, but it was far from obvious for me.
Mar
26
reviewed Approve suggested edit on Proof by Induction $4^n \geq 16n^2$
Mar
26
answered Proof by Induction $4^n \geq 16n^2$
Mar
26
reviewed Approve suggested edit on Proof of Integration formula
Mar
26
reviewed Approve suggested edit on Cauchy-Schwarz Inequality and Linear inependence and $\cos \theta$
Mar
26
awarded  Popular Question
Mar
25
reviewed Approve suggested edit on define $f :R\to R$ by $f(x)=\frac{1}{(x-1)}$ when $x<1$ and $f(x)=\sqrt{(x-1)}$ when $x\geq 1$. Show that $f$ is a bijection and determine its inverse
Mar
25
comment Get the number of subset.
If you mean subsets containing even elements, you should write that; "subsets with an even number of elements" means, unambiguously, "subsets whose number of elements is even".
Mar
25
comment Get the number of subset.
The set $\{1,2,3\}$ has an odd number of elements (namely 3).
Mar
24
comment The rank of general inverse of $A$ times $A$?
How is the general inverse defined? Because $AXA=A$ only implies that the rank of $X$ is at least the rank of $A$.
Mar
24
comment Probability of always rolling 6 on a dice
@ST3 (about the edit): According to Wikipedia, both "die" and "dice" are acceptable as singular.
Mar
24
comment Can a positive function defined on a closed interval have $0$ as an inf?
And $f(a)=0$, therefore the function is not positive.
Mar
24
comment Why does $ (\frac{1}{2})^∞ = 0?$
Indeed. There are infinitely many natural numbers, but all of them are finite.
Mar
24
comment Why does $ (\frac{1}{2})^∞ = 0?$
If you actually reach infinity, you are working in an algebra or field which contains infinity in one way or another. And then I'd expect the value to depend on the exact algebra or field you use. For example, I'd be surprised if in the hyperreal numbers this gives zero instead of an infinitesimal number.