Differential Equation

[Zohreh]

Dear Friends,

I am going to solve the following differential equation:
dY(x)/dx=A*f(x)-B*Y(x)

In which A and B are some parameters, f(x) is a function of x, and Y(C)=0 (C is a parameter).

I tried to solve it in Mathematica by
DSolve[Y'[x] == A*f[x] - B*Y[x], Y[C] == 0, x]

But I get the following error
DSolve::dsfun: "Y[C]==0 cannot be used as a function

I would highly appreciate it if somebody can help me.

Best regards.

[Murray Eisenberg]

Did you make any attempt whatsoever to consult the documentation for the proper syntax of DSolve? The correct syntax is

DSolve[{eqn1, eqn2, ...}, y, x]

or

DSolve[{eqn1, eqn2, ...}, y[x], x]

In your case:

DSolve[{Y'[x] == A*f[x] - B*Y[x], Y[C] == 0}, Y[x], x]

Actually, you should avoid using upper-case letters for your own names, since built-in Mathematica names begin with such. Thus it would be much safer to use:

DSolve[{y'[x] == a f[x] - b y[x], y[c] == 0}, y[x], x]

Post by Zohreh
dY(x)/dx=A*f(x)-B*Y(x)
In which A and B are some parameters, f(x) is a function of x, and Y(C)=0 (C is a parameter).
I tried to solve it in Mathematica by
DSolve[Y'[x] == A*f[x] - B*Y[x], Y[C] == 0, x]
But I get the following error
DSolve::dsfun: "Y[C]==0 cannot be used as a function
I would highly appreciate it if somebody can help me.

Murray Eisenberg ***@math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower phone [phone] (H)
University of Massachusetts
710 North Pleasant Street
Amherst, MA 01003-9305

[psycho_dad]

Hi,
The correct syntax is this:
DSolve[{Y'[x] == A*f[x] - B*Y[x], Y[C] == 0}, Y[x], x]

Notice the brackets {} and the Y[x]. See the help of DSolve for more examples etc.

Cheers

[David Reiss]

Check the syntax for the proper use of DSolve. You are looking for

DSolve[{Y'[x] == A*f[x] - B*Y[x], Y[C] == 0}, Y, x]

Also note that C is a reserved symbol in Mathematica. Generally you should avoide using capital letters for your parameters and functions

Post by Zohreh
Dear Friends,
dY(x)/dx=A*f(x)-B*Y(x)
In which A and B are some parameters, f(x) is a function of x, and Y(C)=0 (C is a parameter).
I tried to solve it in Mathematica by
DSolve[Y'[x] == A*f[x] - B*Y[x], Y[C] == 0, x]
But I get the following error
DSolve::dsfun: "Y[C]==0 cannot be used as a function
I would highly appreciate it if somebody can help me.
Best reards.

C

[Bill Rowe]

Post by Zohreh
dY(x)/dx=A*f(x)-B*Y(x)
In which A and B are some parameters, f(x) is a function of x, and
Y(C)=0 (C is a parameter).
I tried to solve it in Mathematica by DSolve[Y'[x] == A*f[x] -
B*Y[x], Y[C] == 0, x]
But I get the following error DSolve::dsfun: "Y[C]==0 cannot be used
as a function
I would highly appreciate it if somebody can help me.

=46irst, it is unwise to use a single capital letter as a variable
name as many already have built-in meaning such as C. But, this
isn't the specific problem with your example.

Second, did you look at the documentation for DSolve? If you do,
you will notice the second argument needs to be a function not
an equation. So, try

DSolve[y'[x] == a*f[x] - b*y[x] && y[c] == 0, y[x], x]

[Bob Hanlon]

Use correct syntax for DSolve

DSolve[{Y'[x] == A*f[x] - B*Y[x], Y[C] == 0}, Y[x], x]


{{Y[x] -> (-E^((-B)*x))*
(Integrate[A*E^(B*K[1])*
f[K[1]], {K[1], 1,
C}] - Integrate[
A*E^(B*K[1])*f[K[1]],
{K[1], 1, x}])}}


I also recommend that you avoid using capital letters for, or to start,
user-defined names to avoid potential naming conflicts with Mathematica's
built-in symbols.



Bob Hanlon

Post by Zohreh
Dear Friends,
dY(x)/dx=A*f(x)-B*Y(x)
In which A and B are some parameters, f(x) is a function of x, and Y(C)=0
(C is a parameter).
I tried to solve it in Mathematica by
DSolve[Y'[x] == A*f[x] - B*Y[x], Y[C] == 0, x]
But I get the following error
DSolve::dsfun: "Y[C]==0 cannot be used as a function
I would highly appreciate it if somebody can help me.
Best regards.

[Zohreh]

Post by Zohreh
Dear Friends,
dY(x)/dx=A*f(x)-B*Y(x)
In which A and B are some parameters, f(x) is a function of x, and Y(C)=0 (C is a parameter).
I tried to solve it in Mathematica by
DSolve[Y'[x] == A*f[x] - B*Y[x], Y[C] == 0, x]
But I get the following error
DSolve::dsfun: "Y[C]==0 cannot be used as a function
I would highly appreciate it if somebody can help me.
Best regards.

Thanks to all for your help.

Best regards.