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1h
revised Conjugation of permutations
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6h
reviewed Close $L^2$ convergence of this sequence
6h
reviewed Close Verification of the Hormander condition
6h
comment Prove a matrix is non-negative.
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6h
comment The product of two of the four roots of $x^4 -20x^3+ kx^2 + 590x -1992 = 0$ is $24$ the find $k$.
Your question was put on hold, the message above (and possibly comments) should give an explanation why. You might try to edit your question to address these issues. Note that the next edit puts your post in the review queue, where users can vote to reopen this. (Therefore it would be good to avoid minor edits and improve your question as much as possible with the next edit.)
6h
reviewed Close The product of two of the four roots of $x^4 -20x^3+ kx^2 + 590x -1992 = 0$ is $24$ the find $k$.
6h
reviewed Close How many people does the $n$th person know?
6h
reviewed Leave Open Why does $\frac{49}{64}\cos^2 \theta + \cos^2 \theta$ equal $\frac{113}{64}\cos^2 \theta $?
8h
awarded  Popular Question
9h
revised Why is the cartesian product so categorically robust?
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9h
revised Why does $\frac{49}{64}\cos^2 \theta + \cos^2 \theta$ equal $\frac{113}{64}\cos^2 \theta $?
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9h
revised The derivative of $x!$ and its continuity
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19h
revised Prove that $\sin (\theta) + \cos(\theta) \ge 1$
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21h
comment Finding extreme values of a variable on an intersection of a sphere and a plane
I made some edits, thanks for noticing the typos. I have chosen unit vectors as basis in order to preserve lengths. That is why I got $a^2+b^2=1$. For linear expression it can be "seen" that $g(a,b)=3a+b$ increases in the direction $(3,1)$. However, as you are studying multivariable calculus, this can also be explained by noticing that this vector is the gradient.$\nabla g=(3,1)$. But I will certainly admit that was meant more to be "geometrical" than "rigorous".
21h
revised Finding extreme values of a variable on an intersection of a sphere and a plane
deleted 2 characters in body
22h
revised Finding extreme values of a variable on an intersection of a sphere and a plane
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22h
answered Finding extreme values of a variable on an intersection of a sphere and a plane
1d
revised Finding extreme values of a variable on an intersection of a sphere and a plane
edited title
1d
comment How can I show this inequality: $-2 \le \cos \theta (\sin \theta +\sqrt{\sin ^2 \theta +3})\le 2$
Please, try to make the title of your question more informative. E.g., Why does $a<b$ imply $a+c<b+c$? is much more useful for other users than A question about inequality. From How can I ask a good question?: Make your title as descriptive as possible. In many cases one can actually phrase the title as the question, at least in such a way so as to be comprehensible to an expert reader. You can find more tips for choosing a good title here.
1d
revised How can I show this inequality: $-2 \le \cos \theta (\sin \theta +\sqrt{\sin ^2 \theta +3})\le 2$
more descriptive title