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[Axiom-mail] Roots of Polynomials
From: |
Gernot Hueber |
Subject: |
[Axiom-mail] Roots of Polynomials |
Date: |
Tue, 19 Dec 2006 14:36:37 +0100 |
Hi,
I would like to calculate the roots of polynomials with unknown or partly
unknown coefficients. For some rare cases there are solutions known e.g.
Cardans formulas for cubic polynomials, and low order reciprocal polynomials
can be solved.
However I don't know how to achieve this with Axiom.
See some trials below.
However, I guess I should be possible to get more than shown below, but I am
sorry I have no idea how.
Thanks
Gernot
1) Second order polynomial
(5) -> p1 := x**2 + a*x + b
(5) ->
2
(5) x + a x + b
Type: Polynomial Integer
Time: 0 sec
(6) -> zerosOf(p1, x)
(6) ->
+---------+ +---------+
| 2 | 2
\|- 4b + a - a - \|- 4b + a - a
(6) [----------------,------------------]
2 2
Type: List Expression Integer
2) Cubic polynomial
(9) -> p2 := x**3 + a*x**2 + b*x + c
(9) ->
3 2
(9) x + a x + b x + c
Type: Polynomial Integer
Time: 0.01(O) = 0.02 sec
(10) -> zerosOf(p2, x)
(10) ->
(10)
+--------------------------+
| 2 2
\|- 3%x9 - 2a %x9 - 4b + a - %x9 - a
[%x9, ---------------------------------------,
2
+--------------------------+
| 2 2
- \|- 3%x9 - 2a %x9 - 4b + a - %x9 - a
-----------------------------------------]
2
Type: List Expression Integer
Time: 0.02(E) = 0.02 sec
(11) -> definingPolynomial %x9
(11) ->
2 3
(11) c + %x9 b + %x9 a + %x9
Type: Expression Integer
Time: 0 sec
3) Simple reciprocal polynomial
(12) -> p3 := x**3 + a*x**2 + a*x + 1
(12) ->
3 2
(12) x + a x + a x + 1
Type: Polynomial Integer
Time: 0 sec
(13) -> zerosOf(p3, x)
(13) ->
(13)
+----------------------------+
| 2 2
\|- 3%x12 - 2a %x12 + a - 4a - %x12 - a
[%x12, ------------------------------------------,
2
+----------------------------+
| 2 2
- \|- 3%x12 - 2a %x12 + a - 4a - %x12 - a
--------------------------------------------]
2
Type: List Expression Integer
Time: 0.01(O) = 0.02 sec
(14) -> definingPolynomial %x12
(14) ->
2 3
(14) (%x12 + %x12)a + %x12 + 1
Type: Expression Integer
Time: 0 sec
(15) -> rootsOf(p3, x)
(15) ->
(15) [%x15,%x16,- %x16 - %x15 - a]
Type: List Expression Integer
Time: 0.01(O) = 0.02 sec
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