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 Subst

substitute values for indeterminates
 Syntax
 ``` Subst(E:OBJECT, X, F):OBJECT Subst(E:OBJECT,[[X_1, F_1],...,[X_r, F_r]]):OBJECT where each X or X_i is an indeterminate and each F or F_i is a number, polynomial, or rational function. ```

 Description
The first form of this function substitutes F_i for X_i in the expression E. The second form is a shorthand for the first in the case of a single indeterminate. When substituting for the indeterminates in order, it is easier to use Eval .

 Example
 ``` Use R ::= QQ[x,y,z,t]; F := x+y+z+t^2; Subst(F,x,-2); t^2 + y + z - 2 ------------------------------- Subst(F,x,z/y); (yt^2 + y^2 + yz + z)/y ------------------------------- Subst(F,[[x,x^2],[y,y^3],[z,t^5]]); t^5 + y^3 + x^2 + t^2 ------------------------------- Eval(F,[x^2,y^3,t^5]); -- the same thing as above t^5 + y^3 + x^2 + t^2 ------------------------------- MySubst := [[y,1],[t,3z-x]]; Subst(xyzt, MySubst); -- substitute into the function xyzt -x^2z + 3xz^2 ------------------------------- ```