solve for x+y+z if

19x^3+95x+57=0

19y^3+95y+57=0

19z^3+95z+57=0

x,yand z are not equal to each other

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- October 24th 2012, 08:14 PMkahandasaequations help
solve for x+y+z if

19x^3+95x+57=0

19y^3+95y+57=0

19z^3+95z+57=0

x,yand z are not equal to each other - October 24th 2012, 08:16 PMProve ItRe: equations help
- October 24th 2012, 08:26 PMkahandasaRe: equations help
ya but it is very diificullt. the only way is to play with the eqation and obtain x+y+z

- October 24th 2012, 08:43 PMSorobanRe: equations help
Hello, kahandasa!

A very strange problem . . .

Quote:

. .

. .

- October 24th 2012, 08:54 PMkahandasaRe: equations help
i dont understand why x+y+z=0

- October 25th 2012, 05:53 AMzzephodRe: equations help
Viete's relations: the sum of the roots of an n-th degree polynomial equation is -1 times the coefficient of the (n-1)-th degree term divided by the coefficient of the n-th degree term. Since there is no term in the square of the variable and we have a cubic the sum of the roots is zero.

In this case we can be explicit, with soroban's notation:

etc..

Also all the roots are different since by Descartes' rule of signs there are zero positive roots and one negative root, hence exactly one real root, and as this is a polynomial with real coefficients the remaining two complex roots are a conjugate pair and hence not equal.

CB