## 607 Reputation

19 years, 238 days

## How to composite vector functions?...

Maple

I have

f(x,y)=x y+x^2+1

and

g(t)=(2 t, 3 t).

I want to obtain the function (f o g)(t)  as a real-to-real one variable function.

What I tried:

f:=(x,y) -> x y+x^2+1,   it's ok;

g:=t -> <2 t, 3 t>,  it's ok.

But f@g  returns f@g.

How it would be possible to obtain f o g ?

## cubic equation...

Maple

I want to obtain the exact (symbolic) solution of

240*t^3 + 144*t^2 - 135*t -52 =0

in the form  a+ b*I, where a, b are (symbolic) real numbers.

It is possible if I understand Wikipedia well.

"solve" gives "RootOf" and the "convert(......, radical)"  gives quantities such as

(9522 + 45*I* squarerootsymbol(226511))^(1/3)

Thanks.

## Groebner...

Maple

I'm at the very beginning of Goebner bases, so sorry if my question is too elementary or I don't use the correct terminology.

I have polynomials, p1(x1,...,x9), ..., p8(x1,...,x9), and q(x1,...,x9).

I need an algebraic representation of q by p1,....  . Since the answer can be long, it would be useful to obtain the "coefficients" separately also.  One (a bit stupid) example is:

p1(x1,x2):= x1 + x2,  p2:= x1^2 + x2^2,  q(x1,x2):= x1^3 + x2^3.

## RootOf...

Maple

x=RootOf( _Z^2*a+1, label=_L1)*b

Does it mean that

(x/b)^2*a+1=0 ?

Thanks.

## Archive...

The question is simple.

How could I find an earlier (not Active) forum topic?

(I use Firefox 3.5 on xp.)

Thanks,    Sandor

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