# Odd CFactorise result in miss-CAS-interpretation?

Liliana shared this problem 7 years ago

Hi!

Perhaps to go on with the same ticket of one of several sintoms of this type of unexpected results? As https://jira.geogebra.org/b... Perhaps it could be more straight than the tactic of dividing sintoms of the same problem in multiple tickets spread around locked questions?

GeoGebra 4.9.104.0-JOGL1 (14 February 2013) Java: 1.7.0_09

Being:

eo_1 := 1/ (sqrt(1/7) (2 x + ? sqrt(3))) and

eo_1 := 1/ (sqrt(1/7) (2 x + ? sqrt(3)))

CommonDenominator[eo_1,eu_1] gives sqrt(21) - 2sqrt(7) x ? + 3sqrt(3) x² ? + 6x³

CFactorise[sqrt(21) - 2sqrt(7) x ? + 3sqrt(3) x² ? + 6x³] gives (

3x² - ? sqrt(7)) (2x + ? sqrt(3))

But...

CFactorise[CommonDenominator[eo_1,eu_1]] gives

(9x? + 7) (4x² + 3)

Same thing in

GeoGebra 4.2.19.0 (08 February 2013) Java: 1.7.0_09

Thanks so much for any explicative answer. Cheers,

Liliana

[size=85]One of them... such as the previous:

Being ex_1 := (1 / (2 x - 3 p)) and ex_2 := (3 / (4 x² - 4 x p + p x))

CommonDenominator[ex_1, ex_2] gives 9p² x - 18p x² + 8x³

Factorise[9p² x - 18p x² + 8x³] gives (4x - 3p) (2x - 3p) x

But...

Factorise[CommonDenominator[ex_1,ex_2]] gives 1

But... in

GeoGebra 4.2.19.0 (08 February 2013) Java: 1.7.0_09

Factorise[CommonDenominator[ex_1, ex_2]] gives a correct result

(3p - 2x) (3p - 4x) x

However, in both GG versions...

Factorise[CommonDenominator[ (1 / (2 x - 3 p)), (3 / (4 x² - 4 x p + p x)) ]] gives 1

Liliana[/size] 1 ... and also CIFactor

CIFactor[(-x) / 4 pi² + ί sqrt(3 + x) / 2 + x² + 3 / 4] gives -(π + sqrt(4x³ - sqrt(-12 x² - 4x³) + 3x) / x) ("sym2poly/r2sym(const gen & e,const index_m & i,const vecteur & l) Error: Bad Argument Value" + "sym2poly/r2sym(const gen & e,const index_m & i,const vecteur & l) Error: Bad Argument Value") / 4

Liliana

https://ggbm.at/562531 1