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# how to solve system of equations

Posted 8 years ago
 Hi, Can somebody recommend the best way to write mathematica script to solve this system of equations : S=tS + tA(t) +tB(t) +1 A(t)= tC(t) + tE(t) B(t)= tD(t) + tF(t) C(t)= tS(t) + tB(t) D(t)= tS(t) + tA(t) F(t)= tC(t) E(t)= tD(t) Thanks
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Posted 8 years ago
 Very thanks
Posted 8 years ago
 Hi Massimo,Here is some information on using the rules provided by Solve. And also in the attached notebook. In:= (* Solve provided rules which can be used with Replace to \ extract expressions for the vvariables it solved for *) (* /. is a short form of Replace *) In:= s /. generalSolution Out= (-1 + t^2 + t^3)/(-1 + t + t^2 + 2 t^3 + t^4) In:= (* This expression can be used to define a function. I give \ it another name for convenience. *) In:= fs[t_] = s /. generalSolution; In:= (* now it can be used as a function *) In:= fs[a] Out= (-1 + a^2 + a^3)/(-1 + a + a^2 + 2 a^3 + a^4) Attachments:
Posted 8 years ago
 s -> (s /. generalSolution) 
Posted 8 years ago
 Thanks for reply .. but I'd like to have this function: Posted 8 years ago
 generalSolution = Simplify@Solve[{s == t s + t a + t b + 1, a == t c + t e, b == t d + t f, c == t s + t b, d == t s + t a, f == t c, e == t d}][]; s /. generalSolution You can read the documentation on Solve (Examples > Scope > Basic Uses) on how to extract values from a solution in Mathematica format.
Posted 8 years ago
 Now .. How can I refer to the function s?I want to print just this function..Thanks!
Posted 8 years ago
 Great!
Posted 8 years ago
 This is a very unclear question, both in terms of Mathematica and in the underlying mathematics. Here are a few suggestions.(1) Pare it down to a smaller example.(2) Explain clearly what is desired both for input and output.(3) As part of item (2) make sure to explain carefully if this is intended to be a system of differential equations, difference equations, polynomial equations, or womething else entirely.(4) As part of item (3), make sure to explain what you have in mind when mentioning "the s generating function".
Posted 8 years ago
 Sorry, ..anyway the request is solved!Bye!
Posted 8 years ago
 Mathematica is allergic to some big letters.  eqs = { s == t*s + t*a + t*b + 1, a == t*c + t, b == t*d + t*f, c == t*s + t, d == t*s + t*a, f == t*c, e == t*d}; FullSimplify@First@Solve[eqs, {a, b, c, d, e, f, s}, Reals] // Column // TraditionalForm Posted 8 years ago
 This may be what you want: Simplify@Solve[{s == t s + t a + t b + 1, a == t c + t e, b == t d + t f, c == t s + t b, d == t s + t a, f == t c, e == t d}][] Strangely enough, this gives no answer: Solve[{s == t s + t a + t b + 1, a == t c + t e, b == t d + t f, c == t s + t b, d == t s + t a, f == t c, e == t d}, {a, b, c, d, e, f}]