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 Jan1 answered Understanding a “matrix repræsentation” Jan1 reviewed Approve Properties of solutions of system of integral equation. Jan1 reviewed No Action Needed Does the number of elements of order $r$ equal $\sum_{|x| = r} |x^G|$? Jan1 revised A simple proof that $\bigl(1+\frac1n\bigr)^n\leq3-\frac1n$? deleted 49 characters in body Jan1 revised A simple proof that $\bigl(1+\frac1n\bigr)^n\leq3-\frac1n$? added 2 characters in body Jan1 comment A simple proof that $\bigl(1+\frac1n\bigr)^n\leq3-\frac1n$? By multiplying both sides of the second last inequality with $n(n-1)$, we get $-3(n-1) - n + 1 \leq -(n-1)$ which is equivalent to $-3n + 3 - n + 1 \leq -n + 1$, and by adding $3n-3$ to both sides, I ended up with $-n+1 \leq 2n-2$, if you're wondering. It seems simpler to just add $n-1$ to both sides, to retrieve $n \geq 1$ immediately. I changed the answer accordingly. Jan1 comment A simple proof that $\bigl(1+\frac1n\bigr)^n\leq3-\frac1n$? Also, your last line implies that $\frac{3}{n+1} \leq 0$, which is wrong. Jan1 comment A simple proof that $\bigl(1+\frac1n\bigr)^n\leq3-\frac1n$? You have a mistake in your calculations. Note that $$- \frac{n+1}{n(n+1)} - \frac{1}{n(n+1)} = \frac{-n-1-1}{n(n+1)} = -\frac{n+2}{n(n+1)}.$$ Jan1 answered A simple proof that $\bigl(1+\frac1n\bigr)^n\leq3-\frac1n$? Jan1 revised Diagonalization versus s.d. product for non-commuting Hermitian matrices added 112 characters in body; edited tags Jan1 comment Function and sequence How do you get $u_0 > u_1$ in question 5? Jan1 comment Conversion of the Gauss law $\nabla \cdot E = \frac{\rho } {\epsilon_0}$ into integral form Basically, you're going back from Maxwell's first equation $\nabla \cdot E = \frac{\rho}{\epsilon_0}$ to Gauss' law $\Phi_E = \frac{Q}{\epsilon_0}$. As Siminore has pointed out, your notation is a bit problematic. Jan1 reviewed Approve Eigenvectors of $2\times 2$ real symmetric matrix Jan1 comment Cauchy product of two different series What did you try? Jan1 revised What is $\rightarrowtail$ used for? edited tags Jan1 revised Diagonalization versus s.d. product for non-commuting Hermitian matrices deleted 9 characters in body Jan1 comment What is $\rightarrowtail$ used for? Knowing a map is an injection is often better than only knowing it is a map. See: en.wikipedia.org/wiki/Injective_function Jan1 answered What is $\rightarrowtail$ used for? Jan1 answered Diagonalization versus s.d. product for non-commuting Hermitian matrices Jan1 revised Forming contrapositive edited tags