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 Mar19 comment How do i prove that the reduced row echelon form is unique? By "question", I meant your definition of being in reduced row echelon form. I meant that you never defined what it means for $B$ to be the rref of $A$. Mar19 comment How do i prove that the reduced row echelon form is unique? You only defined the property of being in reduced row echelon form. This is a yes/no question. I cannot think of a natural definition for uniqueness from your question. Mar19 comment to show $X$ is disconnected You don't need a concept of a "mother space" to define connectedness - it's all about finding two open subsets $A,B\subset X$ with $A\cap B=\emptyset$ and $A\cup B=X$. Mar19 comment $g:\mathbb{C}\rightarrow\mathbb{C}$ be analytic and $g(0)\neq 0$ we need to calculate $\frac{1}{2\pi i}\int_{|z|=r>0} f(z)g(z) dz$ Calculate residue at 0 using Laurent series? Mar17 answered 7th class question my daughter asked and need answer if possible Mar10 comment Show that $f(z)$ has no antiderivative in $\,S=\mathbb{C}\setminus \{-i,i\}$ @mrf: Then i think it would be more correct to say "You could've also picked an integral around z=-i, because you'd get similar problems", instead of just "repeat". "Repeat" makes it sounds like they're both necessary. Mar10 comment Show that $f(z)$ has no antiderivative in $\,S=\mathbb{C}\setminus \{-i,i\}$ In the third solution, the repetition for $z=-i$ is not necessary - you have already proven that the antiderivative does not exist in the given area. Mar10 comment Show $I=\{sf\mid s\in \mathbb Z_{11}[x]\}$ matches $J=\{h \in \mathbb Z_{11}[x] \mid h(1) = h(-2) = 0\}$. @haunted85: Those are just the roots of $f$. Mar10 revised Show $I=\{sf\mid s\in \mathbb Z_{11}[x]\}$ matches $J=\{h \in \mathbb Z_{11}[x] \mid h(1) = h(-2) = 0\}$. added 14 characters in body Mar10 comment Show $I=\{sf\mid s\in \mathbb Z_{11}[x]\}$ matches $J=\{h \in \mathbb Z_{11}[x] \mid h(1) = h(-2) = 0\}$. $f(\overline 2)=\overline 4$ so $f\not\in J$ but $f\in I$ with $s=1$. So $I\neq J$ Mar10 answered Show $I=\{sf\mid s\in \mathbb Z_{11}[x]\}$ matches $J=\{h \in \mathbb Z_{11}[x] \mid h(1) = h(-2) = 0\}$. Mar10 comment Show $I=\{sf\mid s\in \mathbb Z_{11}[x]\}$ matches $J=\{h \in \mathbb Z_{11}[x] \mid h(1) = h(-2) = 0\}$. In the definition of $I$, don't you mean $s\in\mathbb{Z}_{11}[x]$? Feb9 comment What is inverse of $I+A$? By substituting $A'=A-I$, you are basically asking for the inverse of all matrices. Feb6 comment Example of an increasing, integrable function $f:[0,1]\to\mathbb{R}$ which is discontinuous at all rationals? @Belgi: that depends on your measure... Jan31 comment A box contains 150 oranges.If one orange is taken… @AndréNicolas: I read it as a "factory of boxes" question, in which some process generates uniformly distributed rotten oranges. If you know the probability for this exact box, then apparently you have already counted the rotten ones. Jan31 comment A box contains 150 oranges.If one orange is taken… Strictly speaking, we don't know the number of good oranges. There could be 150 bad oranges in the box. We can only give the estimated number of good oranges. Jan30 comment Algorithm to find the numbers expressible as the sum of two positive cubes in two different ways Of course, in Haskell, you wouldn't need to stop anywhere. You can just calculate them all and print a finite subset. Jan21 comment Filter signal through convolution @Kristian: Oh, then perhaps you haven't reached this yet, but convolution in the time domain is multiplication in the Fourier domain. So just take the Fourier transform of both, multiply, and detransform. Jan21 comment Filter signal through convolution Why don't you use fourier analysis? You correctly tagged it as such. Jan20 comment Solution of integration of $e^{x^2}$ @MårtenW: I must admit I missed that, but of course this can be solved by some appropriate complex substitution.