Examples:

1.         e1 := x^2 - x - 6
           s2 := subs(x=2, e1)
           s4 := subs(x=4, e1)
           s10 := subs(x=1/7, e1)
           d10 := evalf(s10)
         

   

   Comment: Note that the original expression e1 is not changed by the subs command. Each execution of the subs command produces its own new result.

2.         e2 := subs(x=z+3, e1)
           t2 := subs(z=2, e2)
           t4 := subs(z=4, e2)
           t10 := subs(z=1/7, e2)
         

   

   Comment: In the first subs command a new mathematical expression is substituted for x. In the next commands, numerical values are substituted, demonstrating that the subs command will substitute whatever you ask it to substitute.

3.         e3 := subs(x=z^2→-z-6, e1)
           u3 := subs(z=3/7→, e3)
           evalf(u3)
         

   
4. e3 := subs(x=z^2→-z-6, e1)

   Right-click e3 and select Evaluate at a point to substitute z=3/7, then right-click the result and name it u3. Now right-click the result and select Approximate with 10 digits to obtain the decimal result.

   

   Comment: The two different ways to substitute values can be intermixed and the result is the same. Example 3 performs the same tasks but with only commands