5:38 AM
A new tag was created by Burt.
2

I was watching a youtube video on linear algebra and it gave the following equality. $\frac{1}{3}\left(\begin{matrix}1&2\\-1&1\\\end{matrix}\right)\left(\begin{matrix}4\\1\\\end{matrix}\right)=\left(\begin{matrix}2\\-1\\\end{matrix}\right)$ I must be mixing up my basics of matrix multiplication, ...

A new tag was created by Burt. I am pretty sure this tag (or some similar tag) has been discussed before.
-1

Is the set of all polynomials with a degree of at most six and with negative real numbers as coefficients a subspace of $\mathbb{P}_6$? I'm assuming this is asking if a polynomial of up to degree six covers all possibilities that can be produced. How do I determine the answer to this question? *E...

9

There is a tag called subspaces. (It seems that it was created by this user.) Both tag-wiki and tag-excerpt are currently empty, so the usage is unclear.1 If we consider just the name of the tag, there are plenty of situations where it can be used: vector spaces, topological spaces, metric spaces...

8

Update. The subspaces tag has been removed thanks to a friendly neighbourhood Community Manager. There's another possibility that hasn't been mentioned in the OP, and the one I would prefer: kill it! I don't see subspaces as a tag that will ever be consistently used, and not something that ...

8 hours later…
1:50 PM
A new tag was created by tthnew. The tag-info is empty. (It seems to be related to inequalities.)
3

For $a,b,c > 0$ prove: $$(a^2+b^2+c^2)(\frac{1}{a^2}+\frac{1}{b^2}+\frac{1}{c^2}) +\frac{486(ab+bc+ca)^3}{(a+b+c)^6} \geqq 27$$ My work: I can easy found SOS for it: $$\text{LHS-RHS}=\sum {\frac { \left( a-b \right) ^{2}\cdot M}{{a}^{2}{b}^{2} \left( a+b+c \right) ^{6}}} \geqq 0$$ Where $M=\left(... 2:29 PM @MartinSleziak sorry for the delay, I did both. For the Euler things, there is now and I deleted the synonym e to exponential-function There is a also now. The latter may or may not need some clean-up. Checking briefly there is certainly some need for retagging from the latter to the former (or still something else). I did not add the "gamma"; maybe that's an error. We could watch if with the new names misstags still occur. @MartinSleziak I left a comment on Michael's answer directed to OP and him. 2:48 PM @tthnew and Michael: Tangentially what is pqr ? Please somebody write a tag wiki if this should be kept. — quid ♦ 10 mins ago 2 hours later… 4:43 PM @MartinSleziak Based on this answer to the question, it seems to be related to a certain substitution. Since the question is also tagged it seems a bit redundant to me. It also seems to be a bit similar to . 6 hours later… 11:16 PM @quid pqr method have something same as$uvw.$It's let$p=a+b+c,q=ab+bc+ca,r=abc.$It's a nice method like$uvw.\$ — tthnew 18 mins ago