## sorry for the previous massage

Mathematica

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• 1. CountryData[ ]
I can get a list of states in Brazil using CountryData[ ]. CountryData["Brazil","Regions"] I am interested in then getting Polygons that provide a map of these. For example, for all of South America, I can get my graphics with: map["southamerica"]={EdgeForm[Black],Opacity[0],CountryData[#,"Polygon"]&/@C ountryData["SouthAmerica"]} My reading of the documentation suggests that CountryData[ ] does not in fact have geographic information on "Regions" and therefore I am out of luck getting my desired map of the states. Is that right, i.e., I am out of luck? Or am I missing something? If I am out of luck with the IntegratedData, does anyone know a good alternative resource that has lists of longitude and latitude coordinates? Thanks!
• 2. Drop elements from list
Dear group, Consider a list of length, say, 20: a = RandomReal[{},20]; How would you then drop/delete elements, say, 2-5 and 7-10 from this list? The built-in function Drop does not seem to include such a possibility. I should add that I do not have access to Mathematica 7, so any solution should work in version 6. Kind regards, Sigmund
• 3. Subscripts in version 7
Is solved the subscripts problem in version 7?.
• 4. A 3-D Plot Query
Hello, Thanks to every one who helped. I am most grateful. Cheers Sid.
• 5. Combinatorica documentation: Backtrack[]
Hello, Could someone please explain (preferably through an example) how the Backtrack function of the Combinatorica package works? Or even better: point me to the documentation page that describes it? The Combinatorica documentation seems very sparse. I couldn't find anything about Backtrack (apart from the usage message).

### sorry for the previous massage

```a = Lambda[d]/(Lambda[d] + Lambda[in]);

(Lambda[in] / Mu[m]) * (k - 1) +
a* ((1 - a^(n - k)) / (1 - a)) +
(Lambda[in] / Mu[in])* a * ((1 - a^(n -k)) / (1 - a)) +
(Lambda[in] / Mu[M]) * a * (( 1 - a^(n -k)) / (1 - a)) +
(Lambda[d] / Mu[D]) * a^(n - k));
Availability (A)  = P(0,0)*(k + (a * (1-a^(n-k))))

x=(dA/dLambda(in))--->it gives error massages like using inverse function

i use P() only for writing here.  after i take x=(dA/dLambda(in)) i want to find the value using solve[x==0,Lambda(in)] but again i couldn't get any solution..i don't understand what if i do something wrong...

```