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 Oct30 awarded Tumbleweed Oct23 asked Spherical harmonics and convolutions on $S^3$ Sep24 awarded Autobiographer Aug22 answered Almost sure convergence of generalized random harmonic series Aug22 comment Is there a lower bound for $\int_{B_{r}}f$ when $f$ is a positive function? Having $c$ depend of $f$ makes no sense, as then you can take $c = \frac{\int f}{\omega_n r^n}$ to get a tight bound. Aug18 asked Almost sure convergence of generalized random harmonic series May18 awarded Yearling Jan12 awarded Self-Learner Dec27 comment Radius of convergence of $\sum \frac {a_n}{b_n} z^n$ @martycohen: take $x_n = \sqrt[n]{\frac{|a_n|}{|b_n|}}$ and $y_n = \sqrt[n]{|b_n|}$, then apply the inequality I said and divide both sides by $\limsup y_n$. Dec26 comment Is this proof, that $\sqrt{n}$ is irrational for all non-square $n \in \mathbb{N}$, correct or not? It should be $nq^2 = p^2$. Dec26 answered Radius of convergence of $\sum \frac {a_n}{b_n} z^n$ Dec26 answered Show that if $a\neq 0$ in $M_2(\Bbb{R})$, the smallest ideal containing $a$ is the ring itself Dec25 comment How can I find maximum and and minimum values of $f(x,y)=xye^{-(x+y)}$? @MuhammadKhalifaTranCer: see the calculations posted. Dec25 revised How can I find maximum and and minimum values of $f(x,y)=xye^{-(x+y)}$? added 2038 characters in body Dec25 comment How can I find maximum and and minimum values of $f(x,y)=xye^{-(x+y)}$? @MuhammadKhalifaTranCer: I do not know your calculations. Likely you forgot one of the cases somewhere. I can try to post the calculations here, but they are likely to be different from yours, so I can't say whether it is beneficial for you. Dec25 awarded Commentator Dec25 comment How can I find maximum and and minimum values of $f(x,y)=xye^{-(x+y)}$? @MuhammadKhalifaTranCer: Nope. You have $y=0$ or $x=1$. The same goes for $f_y$. But this only gives you the interior points, which according to wolfram happen to not be the maxima and minima in the region. The extrema actually achieved on the boundary, which is the second half of the question. Dec25 comment How can I find maximum and and minimum values of $f(x,y)=xye^{-(x+y)}$? @MuhammadKhalifaTranCer I don't think so. Recheck your computations. Dec25 answered How can I find maximum and and minimum values of $f(x,y)=xye^{-(x+y)}$? Dec25 comment How to find the limits by using series Please write the formula using LaTeX, otherwise it is unclear what you mean.