For a single variable function, I can expand the function 

series(x/(1−x−x^2),x,4);

and get the expansion upto order 4 term.

What shall I do if the function is two variable like f(x,y)=xy/(y−x*sqrt(y)−x^2) and intended to keep terms upto order 5, or moreseries.mw

Download series.mw

say.

My attempt failed as (x^7 + x^5 + x^3 + x)*y etc contains O(8) terms x^7.y

Please help. 

how to write 

-a2/3 + a3 - (2*a4)/3 - (2*a5)/3

into the form 

-(-3*a3 + a2 + 2*a4 + 2*a5)/2

No simplify works. Please help. 

test.mw

How to collect the coefficient of epsilon^(1/2) from A.

Actually, I want to write A as A=c1*epsilon^(1/2) +c2*epsilon+c3*epsilon^(3/2)

How to do that? My collect command failed to do this. 

A:=-epsilon^(3/2)*a2^3/4 - (5*epsilon^(3/2)*a4^3)/3 - (5*epsilon^(3/2)*a5^3)/3 + a3*sqrt(epsilon) - sqrt(epsilon)*a2/3 - (2*sqrt(epsilon)*a4)/3 - (2*sqrt(epsilon)*a5)/3 - (5*epsilon^(3/2)*a2)/36 + (5*epsilon^(3/2)*a4)/9 + (5*epsilon^(3/2)*a5)/9 + epsilon/12 + (4*epsilon^(3/2)*a2*a4*a5)/3 - (7*epsilon^(3/2)*a2*a3*a4)/12 - (7*epsilon^(3/2)*a2*a3*a5)/12 + 5*epsilon^(3/2)*a3*a4*a5 - (3*epsilon^(3/2)*a2^2*a4)/4 - (3*epsilon^(3/2)*a2^2*a5)/4 + (2*epsilon^(3/2)*a2*a4^2)/3 + (2*epsilon^(3/2)*a2*a5^2)/3 - 5*epsilon^(3/2)*a4^2*a5 - 5*epsilon^(3/2)*a4*a5^2 + epsilon^(3/2)*a2^2*a3/12 + (5*epsilon^(3/2)*a3*a4^2)/2 + (5*epsilon^(3/2)*a3*a5^2)/2

I want to modify the code such that it works with

with(LinearAlgebra);
with(VectorCalculus);

How to do that? What is radical? 

with(linalg);
readlib(coeftayl);
A := matrix(2, 2, [0, a, b, 0]);
v := eigenvects(map(eval, A), 'radical');
q := ev[1][3][1];
et := eigenvects(map(eval, transpose(A)), 'radical');
P := et[2][3][1];

How to get a plot where a unit cube [0,1]X[0,1]X[0,1] in R^3 is intersected by a plane $x+z=1$. Please give me a code