6.2.3 Can you answer these questions?

6.2.3.1 How can I modify the code to speed up the `Do`?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=219057

I need to use the following code to do some calculations. But the running speed of this code is too slow. How can I modify this code to improve the running speed? 
 
Cb = 0.5; 
Ch = 5./7; 
 =  ... 
[procedural-programming]
 

asked by Please Correct GrammarMistakeshttps://mathematica.stackexchange.com/landing/r/digest?cta=user&id=42417 1 vote

6.2.3.2 Need help with Limit (DirectedInfinity)

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=219035

I tried to compute the following limit: 
 
Limit[Series[ 
1/(1/x^2) (Sin[y x]/(x^4))^2 - Sin[y x]/y(x^3) + 1/x^2, {x, 0, 5}], 
x -> 0, Assumptions -> {y > 0}] 
 
 
the output : 
 
... 
[calculus-and-analysis] [series-expansion]
 

asked by Johe https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=71663 1 vote

6.2.3.3 How can i use Butterworth filter written in matlab to Mathematica

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=218701

i need help to convert this code written in matlab about Butterworth filter: 
 
%remove high-frequency components by 0.5-h butterworth filter; 
n =2; 
Wn =[1/30/0.5];   %30-min low-pass filter (LPF)% 
... 
[signal-processing]
 

asked by Iman Khaki https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=71671 1 vote