Is there a software to write a linear system of equations (it's actually an optimization problem), and solve it. it's of this kind
minF= Y.Y + w(X.X)+ s(Z.Z) with
Y= a + bI + cD + dI* + eD*
X= f + gI + hD + iI* + jD*
Z= k + lI + mD + nI* + oD*

All lower case are parameters, and adctually they have indices (is there something to write that easily, it's a pain under Word...)
I need to diiferentiate F with respects to I and D, then write I and D as functions of I* and D*. I can do it myself but it takes a really long time and even longer to type it, is there a solver for that??
thanks so much for your help