4.25.1 Top new questions this week

4.25.1.1 Display 10^n as power

https://mathematica.stackexchange.com/questions/148794/display-10n-as-power

 
How can I tell MMA to display input of the form 10^n as $10^n$ and not e.g. as 1000 for $n = 3$ or the rational $\frac{1}{1000}$ for $n = -3$. 
 
This would help to keep tables compact when some  ...
 

- asked by Casimir (13 votes), answered by eldo (10 votes)

4.25.1.2 How to remove unknown zero-width character from string?

https://mathematica.stackexchange.com/questions/148899/how-to-remove-unknown-zero-width-character-from-string

 
I have text that contains a zero-width character that I am not able to remove.  A minimum example is in str below where the character is at the start of the text. 
 
str = "4-6"; 
res = ToExpression /@  ...
 

- asked by Edmund (12 votes), answered by Carl Woll (10 votes)

4.25.1.3 Series sum approximation

https://mathematica.stackexchange.com/questions/149090/series-sum-approximation

 
Since there is no closed formula, as far as I know, to find the sum of 
 
$$\sum _{n=2}^{\infty } \frac{(-1)^n}{\sqrt{\log (n)}}$$ 
 
I used  //N to find an approximation and Mathematica gave me  ...
 

- asked by Raffaele (11 votes), answered by TeM (18 votes)

4.25.1.4 How to extract first 9 rows from every block of 22 rows?

https://mathematica.stackexchange.com/questions/149026/how-to-extract-first-9-rows-from-every-block-of-22-rows

 
I'm working with a list of lists (a large table). 
 
How would I extract the first 9 rows from every 22 rows of this list? 
 
Essentially, I'd like to drop rows 10 to 22, and then 32 to 44, and so on,  ...
 

- asked by musicmaker (11 votes), answered by C. E. (11 votes)

4.25.1.5 Confusion about HoldFirst attribute of Set

https://mathematica.stackexchange.com/questions/148956/confusion-about-holdfirst-attribute-of-set

 
Set has the attribute HoldFirst. 
Expectedly the following does not work, i.e. it does not assign the OwnValue of 3 to x: 
 
In[1]:= {x, y}[[1]] = 3 
 
During evaluation of In[1]:= Set::setps: {x,y} in the  ...
 

- asked by kalix (8 votes), answered by Kuba (10 votes)

4.25.1.6 What algorithm is Mathematica using to find the smallest eigenvalue so quickly?

https://mathematica.stackexchange.com/questions/148759/what-algorithm-is-mathematica-using-to-find-the-smallest-eigenvalue-so-quickly

 
My question is what kind of black magic is Mathematica doing to obtain the correct answer so quickly compared to other programming languages? 
 
Details: 
 
I've written a Mathematica notebook to find the  ...
 

- asked by Daniel Walsh 8votes

4.25.1.7 Simplify expression with Sqrt

https://mathematica.stackexchange.com/questions/149186/simplify-expression-with-sqrt

 
Hi folks I have a simple Simplify[] question 
 
the following expression simplifies nice: 
 
Sqrt[4 (a + b) - 4 c] // Simplify 
2 Sqrt[a + b - c] 
 
 
the next one refuses 
 
Sqrt[4 (a + b) - 4 (c + d)] //  ...
 

- asked by Robert Nowak (6 votes), answered by Shadowray (5 votes)