@Markiyan Hirnyk 

Thank you very much. "simplify" works for me. 

@Preben Alsholm  Thank you very much for your help.

Thank you very much. Both two ways worked.

I am curious about the command "Allvalues". If I execute "allvalues(solve(eq, u))", an error apprears

"Error, invalid input: too many and/or wrong type of arguments passed to allvalues; first unused argument is RootOf(_Z^5+_Z^4+_Z^3+_Z^2+_Z-1, index = 2)"

I tried "animate(complexplot, [[evalf(solve(eq, u))], style = point, symbolsize = 10, color = "red"], frames = 50, K = -1 .. 1, background = unitcircle, scaling = constrained, trace = 20)". And it failed.allvalue.mw

Are there any functions regarding delay differential equations?

Thank you very much for your help!

Thank you very much for your help!

thank you very much for your kind help!

thank you very much for your kind help!

@acer

Thank you very much for your explanation. It is really very helpful.

It is my first time to hear about "atomic identifier".
I look into the help system, and find in the 2D mode, I enter

 f<Ctrl+_>x<Right Arrow><Ctrl+=>
sprintf(%a, %);

the result is  "`#msub(mi(\"f\"),mi(\"x\"))`".

Thank you again for your help!

belief111

Acer, it is really a good example for me to experience the maple.

However, I am not so familiar with maple commands. I can not understand "cat(`#msub(mi("`,F,`"),mi("`,X,`"))`)" and can not find any information about #msub, mi in the help system. Are there any help materials for me to learn about this?

Thank you!

Thanks a lot!

 The reason I asked this question is that I have a system, for expample,

sys:=alpha*<-xt[0,1]+a[11]*xt[1,1]*xt[2,2]*xt[1,2]+a[12]*xt[2,2]^2*xt[1,2],-xt[0,2]+a[21]*xt[1,1]^2+a[22]*xt[2,2]^3>;

and variables are alpha, seq(seq(xt[i,j],i=0..2),j=1,2).

My purpose is to get the coefficients of alpha^(q[0])* x[0,1]^(q[1])*x[1,1]^(q[2])...x[2,2]^(q[7]) when sum(q[i],i=1..7)=n so that I can seperate the sytem into parts with different orders.  In my application, n is  not a large number, usually not larger than 3.

I have tried Rong's method, and it  worked well. I wonder are there some other ways to seperate the system.

Thanks a lot!

 The reason I asked this question is that I have a system, for expample,

sys:=alpha*<-xt[0,1]+a[11]*xt[1,1]*xt[2,2]*xt[1,2]+a[12]*xt[2,2]^2*xt[1,2],-xt[0,2]+a[21]*xt[1,1]^2+a[22]*xt[2,2]^3>;

and variables are alpha, seq(seq(xt[i,j],i=0..2),j=1,2).

My purpose is to get the coefficients of alpha^(q[0])* x[0,1]^(q[1])*x[1,1]^(q[2])...x[2,2]^(q[7]) when sum(q[i],i=1..7)=n so that I can seperate the sytem into parts with different orders.  In my application, n is  not a large number, usually not larger than 3.

I have tried Rong's method, and it  worked well. I wonder are there some other ways to seperate the system.

Thanks a lot! The command "degree" is very helpful.
My main purpose to to get the coefficient of (x^n)*(y^m)*(z^k) in a polynomials, for example, a*x*y+b*x^2*y+c*x*y*z. In order to use the command "coeff", the specific values of n,k and m are needed. That's why i asked the question about how to get the information of the degree of the specific variables. 
I wonder are there gonna be some other ways to do this?

Thanks a lot! The command "degree" is very helpful.
My main purpose to to get the coefficient of (x^n)*(y^m)*(z^k) in a polynomials, for example, a*x*y+b*x^2*y+c*x*y*z. In order to use the command "coeff", the specific values of n,k and m are needed. That's why i asked the question about how to get the information of the degree of the specific variables. 
I wonder are there gonna be some other ways to do this?