Error, (in ODEtools/info) x(t) and x cannot both appear in the given ODE.

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In summary, the conversation is about solving a separable differential equation in Maple. The user encounters an error message stating that "x(t)" and "x" cannot both appear in the given ODE. It is explained that "x(t)" and "x" are different symbols and Maple interprets them differently. The correct way to solve the equation in Maple is to use "x(t)" consistently throughout the equation.
  • #1
Susanne217
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Homework Statement



Hi I am trying to solve a seperable differential equation in Maple

eqn1:=diff(x(t),t)=3*t^2/sqrt(x);

But every time I type

dsolve(eqn1,x(t));

I get the very hurtfull error from Maple

"Error, (in ODEtools/info) x(t) and x cannot both appear in the given ODE."

What am I doing wrong?

I have changed it to

eqn1:=diff(x(t),t)=3*t^2/sqrt(x(t)); and Mapple accepted it...

Is this right?
 
Last edited:
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  • #2
"x(t)" and "x" are different symbols. Maple is interpreting "x(t)" as a function of t and "x" as a constant. It appears to Maple that you are using "x" in two different ways and it will not allow that.
 
  • #3
HallsofIvy said:
"x(t)" and "x" are different symbols. Maple is interpreting "x(t)" as a function of t and "x" as a constant. It appears to Maple that you are using "x" in two different ways and it will not allow that.

Okay why Hallsoftivy could they go ahead and write this in the error insteed :)

But thank you :)

I'm given the differential equation

[tex]\frac{dx}{dt} = \frac{3t^2}{\sqrt{x}}[/tex]

without any initial conditions

the right way to solve this in Maple is the command:
eqn1:=diff(x(t),t)=3*t^2/sqrt(x(t));

??
 
Last edited:
  • #4
? That's what I just said: Maple is telling you that you cannot use the letter "x" in two different meanings and that is how Maple is interpreting what you gave.
 

Related to Error, (in ODEtools/info) x(t) and x cannot both appear in the given ODE.

1. What does the error "Error, (in ODEtools/info) x(t) and x cannot both appear in the given ODE." mean?

This error means that in the given ordinary differential equation (ODE), both the independent variable, t, and the dependent variable, x, are used as the function. This is not allowed in ODEs as it leads to ambiguity in the solution.

2. Why is it not allowed to have both t and x as functions in an ODE?

Having both t and x as functions in an ODE leads to a lack of clarity in the solution. It is not possible to determine which variable is the independent variable and which is the dependent variable, making it difficult to solve the equation.

3. How can I fix this error?

To fix this error, you need to rewrite the ODE so that only one variable (either t or x) appears as a function. This can be done by rearranging the equation or using substitution to eliminate one of the variables.

4. Are there any exceptions to this rule?

Yes, there are some exceptions where both t and x can appear in an ODE. This is typically seen in partial differential equations (PDEs) or systems of equations. However, in most cases, it is recommended to avoid having both t and x as functions in an ODE.

5. Can this error occur in other types of equations?

No, this error is specific to ODEs. In other types of equations, such as algebraic or trigonometric equations, it is possible to have both t and x as functions without any issues.

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