x^3-3*x-1=0 la ecuación
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Solución
Teorema de Cardano-Vieta
es ecuación cúbica reducida
px2+qx+v+x3=0donde
p=abp=0q=acq=−3v=adv=−1Fórmulas de Cardano-Vieta
x1+x2+x3=−px1x2+x1x3+x2x3=qx1x2x3=vx1+x2+x3=0x1x2+x1x3+x2x3=−3x1x2x3=−1
/pi\ / /pi\ ___ /pi\ \ ___ /pi\
cos|--| | sin|--| \/ 3 *cos|--| | \/ 3 *sin|--|
\9 / | \9 / \9 / / 1 \| \9 / / 1 \
x1 = - ------- + I*|- ------- - ------------- + im|----------------------------------|| + ------------- + re|----------------------------------|
2 | 2 2 | _____________ || 2 | _____________ |
| | / ___ / ___\|| | / ___ / ___\|
| | / 1 I*\/ 3 | 1 I*\/ 3 ||| | / 1 I*\/ 3 | 1 I*\/ 3 ||
| |3 / - + ------- *|- - - -------||| |3 / - + ------- *|- - - -------||
\ \\/ 2 2 \ 2 2 /// \\/ 2 2 \ 2 2 //
x1=−2cos(9π)+re(−21−23i)321+23i1+23sin(9π)+i−23cos(9π)−2sin(9π)+im(−21−23i)321+23i1
/pi\ / /pi\ ___ /pi\ \ ___ /pi\
cos|--| | sin|--| \/ 3 *cos|--| | \/ 3 *sin|--|
\9 / | \9 / \9 / / 1 \| \9 / / 1 \
x2 = - ------- + I*|- ------- + ------------- + im|----------------------------------|| - ------------- + re|----------------------------------|
2 | 2 2 | _____________ || 2 | _____________ |
| | / ___ / ___\|| | / ___ / ___\|
| | / 1 I*\/ 3 | 1 I*\/ 3 ||| | / 1 I*\/ 3 | 1 I*\/ 3 ||
| |3 / - + ------- *|- - + -------||| |3 / - + ------- *|- - + -------||
\ \\/ 2 2 \ 2 2 /// \\/ 2 2 \ 2 2 //
x2=re(−21+23i)321+23i1−2cos(9π)−23sin(9π)+iim(−21+23i)321+23i1−2sin(9π)+23cos(9π)
_____________
/ ___
1 / 1 I*\/ 3
x3 = ------------------ + 3 / - + -------
_____________ \/ 2 2
/ ___
/ 1 I*\/ 3
3 / - + -------
\/ 2 2
x3=321+23i1+321+23i
x3 = (1/2 + sqrt(3)*i/2)^(-1/3) + (1/2 + sqrt(3)*i/2)^(1/3)
Suma y producto de raíces
[src]
/pi\ / /pi\ ___ /pi\ \ ___ /pi\ /pi\ / /pi\ ___ /pi\ \ ___ /pi\ _____________
cos|--| | sin|--| \/ 3 *cos|--| | \/ 3 *sin|--| cos|--| | sin|--| \/ 3 *cos|--| | \/ 3 *sin|--| / ___
\9 / | \9 / \9 / / 1 \| \9 / / 1 \ \9 / | \9 / \9 / / 1 \| \9 / / 1 \ 1 / 1 I*\/ 3
- ------- + I*|- ------- - ------------- + im|----------------------------------|| + ------------- + re|----------------------------------| + - ------- + I*|- ------- + ------------- + im|----------------------------------|| - ------------- + re|----------------------------------| + ------------------ + 3 / - + -------
2 | 2 2 | _____________ || 2 | _____________ | 2 | 2 2 | _____________ || 2 | _____________ | _____________ \/ 2 2
| | / ___ / ___\|| | / ___ / ___\| | | / ___ / ___\|| | / ___ / ___\| / ___
| | / 1 I*\/ 3 | 1 I*\/ 3 ||| | / 1 I*\/ 3 | 1 I*\/ 3 || | | / 1 I*\/ 3 | 1 I*\/ 3 ||| | / 1 I*\/ 3 | 1 I*\/ 3 || / 1 I*\/ 3
| |3 / - + ------- *|- - - -------||| |3 / - + ------- *|- - - -------|| | |3 / - + ------- *|- - + -------||| |3 / - + ------- *|- - + -------|| 3 / - + -------
\ \\/ 2 2 \ 2 2 /// \\/ 2 2 \ 2 2 // \ \\/ 2 2 \ 2 2 /// \\/ 2 2 \ 2 2 // \/ 2 2
re(−21+23i)321+23i1−2cos(9π)−23sin(9π)+iim(−21+23i)321+23i1−2sin(9π)+23cos(9π)+−2cos(9π)+re(−21−23i)321+23i1+23sin(9π)+i−23cos(9π)−2sin(9π)+im(−21−23i)321+23i1+321+23i1+321+23i
_____________ / /pi\ ___ /pi\ \ / /pi\ ___ /pi\ \
/ ___ | sin|--| \/ 3 *cos|--| | | sin|--| \/ 3 *cos|--| |
1 / 1 I*\/ 3 /pi\ | \9 / \9 / / 1 \| | \9 / \9 / / 1 \| / 1 \ / 1 \
------------------ + 3 / - + ------- - cos|--| + I*|- ------- + ------------- + im|----------------------------------|| + I*|- ------- - ------------- + im|----------------------------------|| + re|----------------------------------| + re|----------------------------------|
_____________ \/ 2 2 \9 / | 2 2 | _____________ || | 2 2 | _____________ || | _____________ | | _____________ |
/ ___ | | / ___ / ___\|| | | / ___ / ___\|| | / ___ / ___\| | / ___ / ___\|
/ 1 I*\/ 3 | | / 1 I*\/ 3 | 1 I*\/ 3 ||| | | / 1 I*\/ 3 | 1 I*\/ 3 ||| | / 1 I*\/ 3 | 1 I*\/ 3 || | / 1 I*\/ 3 | 1 I*\/ 3 ||
3 / - + ------- | |3 / - + ------- *|- - + -------||| | |3 / - + ------- *|- - - -------||| |3 / - + ------- *|- - + -------|| |3 / - + ------- *|- - - -------||
\/ 2 2 \ \\/ 2 2 \ 2 2 /// \ \\/ 2 2 \ 2 2 /// \\/ 2 2 \ 2 2 // \\/ 2 2 \ 2 2 //
−cos(9π)+re(−21+23i)321+23i1+re(−21−23i)321+23i1+321+23i1+iim(−21+23i)321+23i1−2sin(9π)+23cos(9π)+i−23cos(9π)−2sin(9π)+im(−21−23i)321+23i1+321+23i
/ /pi\ / /pi\ ___ /pi\ \ ___ /pi\ \ / /pi\ / /pi\ ___ /pi\ \ ___ /pi\ \ / _____________\
| cos|--| | sin|--| \/ 3 *cos|--| | \/ 3 *sin|--| | | cos|--| | sin|--| \/ 3 *cos|--| | \/ 3 *sin|--| | | / ___ |
| \9 / | \9 / \9 / / 1 \| \9 / / 1 \| | \9 / | \9 / \9 / / 1 \| \9 / / 1 \| | 1 / 1 I*\/ 3 |
|- ------- + I*|- ------- - ------------- + im|----------------------------------|| + ------------- + re|----------------------------------||*|- ------- + I*|- ------- + ------------- + im|----------------------------------|| - ------------- + re|----------------------------------||*|------------------ + 3 / - + ------- |
| 2 | 2 2 | _____________ || 2 | _____________ || | 2 | 2 2 | _____________ || 2 | _____________ || | _____________ \/ 2 2 |
| | | / ___ / ___\|| | / ___ / ___\|| | | | / ___ / ___\|| | / ___ / ___\|| | / ___ |
| | | / 1 I*\/ 3 | 1 I*\/ 3 ||| | / 1 I*\/ 3 | 1 I*\/ 3 ||| | | | / 1 I*\/ 3 | 1 I*\/ 3 ||| | / 1 I*\/ 3 | 1 I*\/ 3 ||| | / 1 I*\/ 3 |
| | |3 / - + ------- *|- - - -------||| |3 / - + ------- *|- - - -------||| | | |3 / - + ------- *|- - + -------||| |3 / - + ------- *|- - + -------||| |3 / - + ------- |
\ \ \\/ 2 2 \ 2 2 /// \\/ 2 2 \ 2 2 /// \ \ \\/ 2 2 \ 2 2 /// \\/ 2 2 \ 2 2 /// \\/ 2 2 /
−2cos(9π)+re(−21−23i)321+23i1+23sin(9π)+i−23cos(9π)−2sin(9π)+im(−21−23i)321+23i1re(−21+23i)321+23i1−2cos(9π)−23sin(9π)+iim(−21+23i)321+23i1−2sin(9π)+23cos(9π)321+23i1+321+23i
/ / 5*pi*I\ -5*pi*I\
| | ------| -------|
| | 9 | 18 | /pi\
2*\-1 + I*\1 - e /*e /*cos|--|
\9 /
2(−1+i(1−e95iπ)e−185iπ)cos(9π)
2*(-1 + i*(1 - exp(5*pi*i/9))*exp(-5*pi*i/18))*cos(pi/9)