x^3+2x^2+9x-18=0 la ecuación
El profesor se sorprenderá mucho al ver tu solución correcta😉
Solución
Teorema de Cardano-Vieta
es ecuación cúbica reducida
px2+qx+v+x3=0donde
p=abp=2q=acq=9v=adv=−18Fórmulas de Cardano-Vieta
x1+x2+x3=−px1x2+x1x3+x2x3=qx1x2x3=vx1+x2+x3=−2x1x2+x1x3+x2x3=9x1x2x3=−18
Gráfica
________________ / ________________\
/ ______ | / ______ |
/ 316 \/ 1383 | ___ / 316 \/ 1383 |
3 / --- + -------- | ___ \/ 3 *3 / --- + -------- |
2 \/ 27 3 23 | 23*\/ 3 \/ 27 3 |
x1 = - - - --------------------- + ------------------------ + I*|- ------------------------ - ---------------------------|
3 2 ________________ | ________________ 2 |
/ ______ | / ______ |
/ 316 \/ 1383 | / 316 \/ 1383 |
18*3 / --- + -------- | 18*3 / --- + -------- |
\/ 27 3 \ \/ 27 3 /
x1=−2327316+31383−32+18327316+3138323+i−23327316+31383−18327316+31383233
________________ / ________________ \
/ ______ | / ______ |
/ 316 \/ 1383 | ___ / 316 \/ 1383 |
3 / --- + -------- |\/ 3 *3 / --- + -------- ___ |
2 \/ 27 3 23 | \/ 27 3 23*\/ 3 |
x2 = - - - --------------------- + ------------------------ + I*|--------------------------- + ------------------------|
3 2 ________________ | 2 ________________|
/ ______ | / ______ |
/ 316 \/ 1383 | / 316 \/ 1383 |
18*3 / --- + -------- | 18*3 / --- + -------- |
\/ 27 3 \ \/ 27 3 /
x2=−2327316+31383−32+18327316+3138323+i18327316+31383233+23327316+31383
________________
/ ______
2 / 316 \/ 1383 23
x3 = - - + 3 / --- + -------- - -----------------------
3 \/ 27 3 ________________
/ ______
/ 316 \/ 1383
9*3 / --- + --------
\/ 27 3
x3=−9327316+3138323−32+327316+31383
x3 = -23/(9*(316/27 + sqrt(1383)/3)^(1/3)) - 2/3 + (316/27 + sqrt(1383)/3)^(1/3)
Suma y producto de raíces
[src]
________________ / ________________\ ________________ / ________________ \
/ ______ | / ______ | / ______ | / ______ |
/ 316 \/ 1383 | ___ / 316 \/ 1383 | / 316 \/ 1383 | ___ / 316 \/ 1383 | ________________
3 / --- + -------- | ___ \/ 3 *3 / --- + -------- | 3 / --- + -------- |\/ 3 *3 / --- + -------- ___ | / ______
2 \/ 27 3 23 | 23*\/ 3 \/ 27 3 | 2 \/ 27 3 23 | \/ 27 3 23*\/ 3 | 2 / 316 \/ 1383 23
- - - --------------------- + ------------------------ + I*|- ------------------------ - ---------------------------| + - - - --------------------- + ------------------------ + I*|--------------------------- + ------------------------| + - - + 3 / --- + -------- - -----------------------
3 2 ________________ | ________________ 2 | 3 2 ________________ | 2 ________________| 3 \/ 27 3 ________________
/ ______ | / ______ | / ______ | / ______ | / ______
/ 316 \/ 1383 | / 316 \/ 1383 | / 316 \/ 1383 | / 316 \/ 1383 | / 316 \/ 1383
18*3 / --- + -------- | 18*3 / --- + -------- | 18*3 / --- + -------- | 18*3 / --- + -------- | 9*3 / --- + --------
\/ 27 3 \ \/ 27 3 / \/ 27 3 \ \/ 27 3 / \/ 27 3
−9327316+3138323−32+327316+31383+−2327316+31383−32+18327316+3138323+i−23327316+31383−18327316+31383233+−2327316+31383−32+18327316+3138323+i18327316+31383233+23327316+31383
/ ________________ \ / ________________\
| / ______ | | / ______ |
| ___ / 316 \/ 1383 | | ___ / 316 \/ 1383 |
|\/ 3 *3 / --- + -------- ___ | | ___ \/ 3 *3 / --- + -------- |
| \/ 27 3 23*\/ 3 | | 23*\/ 3 \/ 27 3 |
-2 + I*|--------------------------- + ------------------------| + I*|- ------------------------ - ---------------------------|
| 2 ________________| | ________________ 2 |
| / ______ | | / ______ |
| / 316 \/ 1383 | | / 316 \/ 1383 |
| 18*3 / --- + -------- | | 18*3 / --- + -------- |
\ \/ 27 3 / \ \/ 27 3 /
−2+i−23327316+31383−18327316+31383233+i18327316+31383233+23327316+31383
/ ________________ / ________________\\ / ________________ / ________________ \\
| / ______ | / ______ || | / ______ | / ______ ||
| / 316 \/ 1383 | ___ / 316 \/ 1383 || | / 316 \/ 1383 | ___ / 316 \/ 1383 || / ________________ \
| 3 / --- + -------- | ___ \/ 3 *3 / --- + -------- || | 3 / --- + -------- |\/ 3 *3 / --- + -------- ___ || | / ______ |
| 2 \/ 27 3 23 | 23*\/ 3 \/ 27 3 || | 2 \/ 27 3 23 | \/ 27 3 23*\/ 3 || | 2 / 316 \/ 1383 23 |
|- - - --------------------- + ------------------------ + I*|- ------------------------ - ---------------------------||*|- - - --------------------- + ------------------------ + I*|--------------------------- + ------------------------||*|- - + 3 / --- + -------- - -----------------------|
| 3 2 ________________ | ________________ 2 || | 3 2 ________________ | 2 ________________|| | 3 \/ 27 3 ________________|
| / ______ | / ______ || | / ______ | / ______ || | / ______ |
| / 316 \/ 1383 | / 316 \/ 1383 || | / 316 \/ 1383 | / 316 \/ 1383 || | / 316 \/ 1383 |
| 18*3 / --- + -------- | 18*3 / --- + -------- || | 18*3 / --- + -------- | 18*3 / --- + -------- || | 9*3 / --- + -------- |
\ \/ 27 3 \ \/ 27 3 // \ \/ 27 3 \ \/ 27 3 // \ \/ 27 3 /
−2327316+31383−32+18327316+3138323+i18327316+31383233+23327316+31383−2327316+31383−32+18327316+3138323+i−23327316+31383−18327316+31383233−9327316+3138323−32+327316+31383
x1 = -1.66854774542557 + 3.26771537233461*i
x2 = -1.66854774542557 - 3.26771537233461*i