Maple 9 Learning Guide - Maplesoft

2.6 Expression Manipulation • 41Common Questions about Expression Manipulation1. How do I substitute for a product of two unknowns? Use siderelations to specify an identity. Substituting directly does not usuallywork because Maple searches for an exact match before substituting.> expr := a^3*b^2;expr := a 3 b 2> subs(a*b=5, expr);a 3 b 2The subs command was unsuccessful in its attempt to substitute. Use thesimplify command.> simplify(expr, {a*b=5});25 aYou can also use the algsubs command, which performs an algebraicsubstitution.> algsubs(a*b=5, expr);25 a2. How do I factor out the constant from 2x + 2y? Currently, thisoperation is not possible in Maple because its simplifier automaticallydistributes the number over the product, believing that a sum is simplerthan a product. In most cases, this is true.If you enter the following expression, Maple automatically multipliesthe constant into the expression.> 2*(x + y);2 x + 2 yHow can you then deal with such expressions, when you need to factorout constants, or negative signs? To factor such expressions, try this substitution.