12.12.1 Top new questions this week

12.12.1.1 Sweetened syntax for uncoupled systems of ODEs in NDSolve[]
12.12.1.2 Upgrading legacy polyhedra code
12.12.1.3 Why does NMinimize report unbounded for $-1 \leq y^3 \leq 1$ but not for the equivalent linear constraint?
12.12.1.4 Why does NMinimize fail with Method -> "Gurobi" for this constrained problem?
12.12.1.5 FindInstance returns no solution when solving for odd integers
12.12.1.6 All curves after the first lose their transparency after export to PDF
12.12.1.7 Folding (hiding) parts of code
12.12.1.1 Sweetened syntax for uncoupled systems of ODEs in NDSolve[]

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=319122

I just discovered the following "works": 
... 
[differential-equations] [numerical-integration] [undocumented]
 
asked by Michael E2 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4999 Score of 7
answered by Michael E2 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4999 Score of 7
12.12.1.2 Upgrading legacy polyhedra code

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=319094

The following code runs in version 4.0 but fails in version 14.0. 
How can I fix it to work in modern versions of Mathematica? 
... 
[graphics3d] [compatibility] [polyhedra]
 
asked by Linda https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=43679 Score of 7
answered by azerbajdzan https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=53172 Score of 4
12.12.1.3 Why does NMinimize report unbounded for $-1 \leq y^3 \leq 1$ but not for the equivalent linear constraint?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=319102

I encountered an inconsistency when using  NMinimize  with constraints that are mathematically equivalent. 
Consider the following examples: 
... 
[mathematical-optimization] [bugs]
                                                                                  

                                                                                  
 
asked by internet https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=87122 Score of 6
answered by Michael E2 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4999 Score of 2
12.12.1.4 Why does NMinimize fail with Method -> "Gurobi" for this constrained problem?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=319134

I am trying to solve the following optimization problem using  NMinimize  with the  "Gurobi"  method: 
... 
[mathematical-optimization]
 
asked by internet https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=87122 Score of 5
answered by Domen https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=75628 Score of 5
12.12.1.5 FindInstance returns no solution when solving for odd integers

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=319127

In a question on Mathematics SE, a comment observes that Mathematica 14.3 reports non-solvability of (a relaxation of) the given problem 
 
Is there an odd $a \neq 1$ s.t. $2^k + 1 | a^k - 1$ for all $k ... 
[findinstance]
 
asked by Eric Towers https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=16237 Score of 4
answered by Michael E2 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4999 Score of 7
12.12.1.6 All curves after the first lose their transparency after export to PDF

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=319110

... 
[plotting] [pdf-format] [opacity]
 
asked by WillG https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=59634 Score of 4
answered by Domen https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=75628 Score of 3
12.12.1.7 Folding (hiding) parts of code

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=319114

By writing some long code ( Module[...] ,  Block[...] , etc.) placed within one cell, it's difficult to promptly operate it (... 
[front-end]
 
asked by Yuri https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=102384 Score of 3