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16h
reviewed Approve Solve L'Hopitals problem
16h
answered Is there a way to simplify…
17h
comment Numbers between $200$ and $1200$ that can be formed with the digits $0,1,2,3 $
is 230 allowed (because it is built by 2,3 and 0) or is it not allowed ( because it is viewed as 0230 and therefore the digit 0 is used two times)?
1d
revised Prove $b>1, r>0 \implies b^r > 1$
typo
1d
answered Prove $b>1, r>0 \implies b^r > 1$
2d
revised Prove $b>1, r>0 \implies b^r > 1$
added 573 characters in body
2d
comment Prove $b>1, r>0 \implies b^r > 1$
You shoul add your comment about what you can already use to your question, because it essential for the answerers to know about it.
Aug
31
reviewed Approve a certain simple continued fraction
Aug
24
revised Geometric sequence problem
latex
Aug
20
answered Interesting and unexpected applications of $\pi$
Aug
16
comment $u=xf(xy)$, show that $xu_{xx}-yu_{xy} = 0$
So please post the solution as an answer
Aug
16
comment $u=xf(xy)$, show that $xu_{xx}-yu_{xy} = 0$
There is no $f_{xx}$ or $f_{xy}$ but only an $f'$ or $f''$
Aug
16
comment $u=xf(xy)$, show that $xu_{xx}-yu_{xy} = 0$
your calculation of $u_x$ is wrong. Choose $u(x,y)=f(xy)=c$ then you get $u_x=c$ and that is wrong.
Aug
16
revised If $3x^2 -2x+7=0$ then $(x-\frac{1}{3})^2 =$?
format, typos wording
Aug
4
comment Difference between ${2\over 9}$ and ${22\over 99}$?
calculate their difference!
Aug
3
comment Prove that the Mandelbrot Set Is A Closed Set
the intersection of closed sets is closed.
Jul
31
reviewed Reject Second differential of the norm in an infinite dimensional Hilbert space
Jul
27
comment Weird Induction…?
your second formula is apparerently wong: it says that $\binom{n + k + 1}{k}$ is constant, independent of $k$. So check your formula, you made an error. It is $$\sum_{i = 0}^{k} \binom{n + i}{i} = \binom{n + k + 1}{k}$$ for $0 \leq k \leq n$
Jul
16
revised Calculate 2000! (mod 2003)
latex, mod
Jul
16
comment Calculate 2000! (mod 2003)
Of course you have to prove that 2003 is a prime otherwise you can't be sure that the result is true.