Advice: Assume doesn't affect solve

The assume command is used with symbolic variables that are not assigned values, and tells Maple that it can apply rules that would be appropriate when the variable has certain properties (e.g. is an integer). This primarily affects the simplify command. Thus if x is assumed to be positive, [Maple Math] can be simplified to [Maple Math] .

However, these assumptions do not restrict the values for x that can be returned by solve and its related commands. There are other ways to restrict these values.

Examples:

> assume(x, positive);

> simplify(sqrt(x^2));

[Maple Math]

In this example, solve finds both real and complex solutions; the assumption on x has no effect.

> solve(x^4 + 2*x = 20, x);

[Maple Math]
[Maple Math]
[Maple Math]
[Maple Math]
[Maple Math]
[Maple Math]
[Maple Math]
[Maple Math]
[Maple Math]
[Maple Math]

Finding positive solutions in "solve":

> solve({y^4 + 2*y = 20, y > 0}, y);

[Maple Math]

Finding real solutions:

> solve({y^4 + 2*y = 20, y > -infinity}, y);

[Maple Math]
[Maple Math]
[Maple Math]

Finding integer solutions:

> isolve(y^4 + 2*y = 20);

[Maple Math]

Real (numerical) solutions with fsolve:

> fsolve(y^4 + 2*y = 20, y);

[Maple Math]

Restricting to an interval:

> fsolve(y^4 + 2*y = 20, y = 0 .. infinity);

[Maple Math]

See also: assume , Declaring the type of an argument , fsolve , isolve , solve

Maple Advisor Database R. Israel, 1997