x^3-3x^2+5 equation
The teacher will be very surprised to see your correct solution 😉
The solution
Vieta's Theorem
it is reduced cubic equation
px2+x3+qx+v=0where
p=abp=−3q=acq=0v=adv=5Vieta Formulas
x1+x2+x3=−px1x2+x1x3+x2x3=qx1x2x3=vx1+x2+x3=3x1x2+x1x3+x2x3=0x1x2x3=5
The graph
_______________ / _______________\
/ ___ | / ___ |
/ 81 27*\/ 5 | ___ / 81 27*\/ 5 |
3 / -- + -------- | ___ \/ 3 *3 / -- + -------- |
\/ 2 2 3 | 3*\/ 3 \/ 2 2 |
x1 = 1 + -------------------- + ---------------------- + I*|- ---------------------- + --------------------------|
6 _______________ | _______________ 6 |
/ ___ | / ___ |
/ 81 27*\/ 5 | / 81 27*\/ 5 |
2*3 / -- + -------- | 2*3 / -- + -------- |
\/ 2 2 \ \/ 2 2 /
x1=232275+2813+632275+281+1+i−232275+28133+6332275+281
_______________ / _______________ \
/ ___ | / ___ |
/ 81 27*\/ 5 | ___ / 81 27*\/ 5 |
3 / -- + -------- | \/ 3 *3 / -- + -------- ___ |
\/ 2 2 3 | \/ 2 2 3*\/ 3 |
x2 = 1 + -------------------- + ---------------------- + I*|- -------------------------- + ----------------------|
6 _______________ | 6 _______________|
/ ___ | / ___ |
/ 81 27*\/ 5 | / 81 27*\/ 5 |
2*3 / -- + -------- | 2*3 / -- + -------- |
\/ 2 2 \ \/ 2 2 /
x2=232275+2813+632275+281+1+i−6332275+281+232275+28133
_______________
/ ___
/ 81 27*\/ 5
3 / -- + --------
3 \/ 2 2
x3 = 1 - -------------------- - --------------------
_______________ 3
/ ___
/ 81 27*\/ 5
3 / -- + --------
\/ 2 2
x3=−332275+281−32275+2813+1
Sum and product of roots
[src]
_______________ / _______________\ _______________ / _______________ \ _______________
/ ___ | / ___ | / ___ | / ___ | / ___
/ 81 27*\/ 5 | ___ / 81 27*\/ 5 | / 81 27*\/ 5 | ___ / 81 27*\/ 5 | / 81 27*\/ 5
3 / -- + -------- | ___ \/ 3 *3 / -- + -------- | 3 / -- + -------- | \/ 3 *3 / -- + -------- ___ | 3 / -- + --------
\/ 2 2 3 | 3*\/ 3 \/ 2 2 | \/ 2 2 3 | \/ 2 2 3*\/ 3 | 3 \/ 2 2
0 + 1 + -------------------- + ---------------------- + I*|- ---------------------- + --------------------------| + 1 + -------------------- + ---------------------- + I*|- -------------------------- + ----------------------| + 1 - -------------------- - --------------------
6 _______________ | _______________ 6 | 6 _______________ | 6 _______________| _______________ 3
/ ___ | / ___ | / ___ | / ___ | / ___
/ 81 27*\/ 5 | / 81 27*\/ 5 | / 81 27*\/ 5 | / 81 27*\/ 5 | / 81 27*\/ 5
2*3 / -- + -------- | 2*3 / -- + -------- | 2*3 / -- + -------- | 2*3 / -- + -------- | 3 / -- + --------
\/ 2 2 \ \/ 2 2 / \/ 2 2 \ \/ 2 2 / \/ 2 2
−332275+281−32275+2813+1+232275+2813+632275+281+1+i−6332275+281+232275+28133+0+232275+2813+632275+281+1+i−232275+28133+6332275+281
/ _______________\ / _______________ \
| / ___ | | / ___ |
| ___ / 81 27*\/ 5 | | ___ / 81 27*\/ 5 |
| ___ \/ 3 *3 / -- + -------- | | \/ 3 *3 / -- + -------- ___ |
| 3*\/ 3 \/ 2 2 | | \/ 2 2 3*\/ 3 |
3 + I*|- ---------------------- + --------------------------| + I*|- -------------------------- + ----------------------|
| _______________ 6 | | 6 _______________|
| / ___ | | / ___ |
| / 81 27*\/ 5 | | / 81 27*\/ 5 |
| 2*3 / -- + -------- | | 2*3 / -- + -------- |
\ \/ 2 2 / \ \/ 2 2 /
3+i−6332275+281+232275+28133+i−232275+28133+6332275+281
/ _______________ / _______________\\ / _______________ / _______________ \\ / _______________\
| / ___ | / ___ || | / ___ | / ___ || | / ___ |
| / 81 27*\/ 5 | ___ / 81 27*\/ 5 || | / 81 27*\/ 5 | ___ / 81 27*\/ 5 || | / 81 27*\/ 5 |
| 3 / -- + -------- | ___ \/ 3 *3 / -- + -------- || | 3 / -- + -------- | \/ 3 *3 / -- + -------- ___ || | 3 / -- + -------- |
| \/ 2 2 3 | 3*\/ 3 \/ 2 2 || | \/ 2 2 3 | \/ 2 2 3*\/ 3 || | 3 \/ 2 2 |
1*|1 + -------------------- + ---------------------- + I*|- ---------------------- + --------------------------||*|1 + -------------------- + ---------------------- + I*|- -------------------------- + ----------------------||*|1 - -------------------- - --------------------|
| 6 _______________ | _______________ 6 || | 6 _______________ | 6 _______________|| | _______________ 3 |
| / ___ | / ___ || | / ___ | / ___ || | / ___ |
| / 81 27*\/ 5 | / 81 27*\/ 5 || | / 81 27*\/ 5 | / 81 27*\/ 5 || | / 81 27*\/ 5 |
| 2*3 / -- + -------- | 2*3 / -- + -------- || | 2*3 / -- + -------- | 2*3 / -- + -------- || | 3 / -- + -------- |
\ \/ 2 2 \ \/ 2 2 // \ \/ 2 2 \ \/ 2 2 // \ \/ 2 2 /
1⋅232275+2813+632275+281+1+i−232275+28133+6332275+281232275+2813+632275+281+1+i−6332275+281+232275+28133−332275+281−32275+2813+1
x2 = 2.05190170136777 - 0.565235851677171*i
x3 = 2.05190170136777 + 0.565235851677171*i
x3 = 2.05190170136777 + 0.565235851677171*i