The teacher will be very surprised to see your correct solution 😉
x1 = -1
_________________ / _________________\ 3 / _____ | ___ ___ 3 / _____ | 1 1 \/ 125 + 9*\/ 193 | \/ 3 \/ 3 *\/ 125 + 9*\/ 193 | x2 = - - ---------------------- + -------------------- + I*|---------------------- + --------------------------| 3 _________________ 6 | _________________ 6 | 3 / _____ | 3 / _____ | 3*\/ 125 + 9*\/ 193 \3*\/ 125 + 9*\/ 193 /
_________________ / _________________\ 3 / _____ | ___ ___ 3 / _____ | 1 1 \/ 125 + 9*\/ 193 | \/ 3 \/ 3 *\/ 125 + 9*\/ 193 | x3 = - - ---------------------- + -------------------- + I*|- ---------------------- - --------------------------| 3 _________________ 6 | _________________ 6 | 3 / _____ | 3 / _____ | 3*\/ 125 + 9*\/ 193 \ 3*\/ 125 + 9*\/ 193 /
_________________ 3 / _____ 1 \/ 125 + 9*\/ 193 2 x4 = - - -------------------- + ---------------------- 3 3 _________________ 3 / _____ 3*\/ 125 + 9*\/ 193
x4 = -(125 + 9*sqrt(193))^(1/3)/3 + 2/(3*(125 + 9*sqrt(193))^(1/3)) + 1/3
sum
_________________ / _________________\ _________________ / _________________\ _________________ 3 / _____ | ___ ___ 3 / _____ | 3 / _____ | ___ ___ 3 / _____ | 3 / _____ 1 1 \/ 125 + 9*\/ 193 | \/ 3 \/ 3 *\/ 125 + 9*\/ 193 | 1 1 \/ 125 + 9*\/ 193 | \/ 3 \/ 3 *\/ 125 + 9*\/ 193 | 1 \/ 125 + 9*\/ 193 2 -1 + - - ---------------------- + -------------------- + I*|---------------------- + --------------------------| + - - ---------------------- + -------------------- + I*|- ---------------------- - --------------------------| + - - -------------------- + ---------------------- 3 _________________ 6 | _________________ 6 | 3 _________________ 6 | _________________ 6 | 3 3 _________________ 3 / _____ | 3 / _____ | 3 / _____ | 3 / _____ | 3 / _____ 3*\/ 125 + 9*\/ 193 \3*\/ 125 + 9*\/ 193 / 3*\/ 125 + 9*\/ 193 \ 3*\/ 125 + 9*\/ 193 / 3*\/ 125 + 9*\/ 193
=
/ _________________\ / _________________\ | ___ ___ 3 / _____ | | ___ ___ 3 / _____ | | \/ 3 \/ 3 *\/ 125 + 9*\/ 193 | | \/ 3 \/ 3 *\/ 125 + 9*\/ 193 | I*|- ---------------------- - --------------------------| + I*|---------------------- + --------------------------| | _________________ 6 | | _________________ 6 | | 3 / _____ | | 3 / _____ | \ 3*\/ 125 + 9*\/ 193 / \3*\/ 125 + 9*\/ 193 /
product
/ _________________ / _________________\\ / _________________ / _________________\\ / _________________ \ | 3 / _____ | ___ ___ 3 / _____ || | 3 / _____ | ___ ___ 3 / _____ || | 3 / _____ | |1 1 \/ 125 + 9*\/ 193 | \/ 3 \/ 3 *\/ 125 + 9*\/ 193 || |1 1 \/ 125 + 9*\/ 193 | \/ 3 \/ 3 *\/ 125 + 9*\/ 193 || |1 \/ 125 + 9*\/ 193 2 | -|- - ---------------------- + -------------------- + I*|---------------------- + --------------------------||*|- - ---------------------- + -------------------- + I*|- ---------------------- - --------------------------||*|- - -------------------- + ----------------------| |3 _________________ 6 | _________________ 6 || |3 _________________ 6 | _________________ 6 || |3 3 _________________| | 3 / _____ | 3 / _____ || | 3 / _____ | 3 / _____ || | 3 / _____ | \ 3*\/ 125 + 9*\/ 193 \3*\/ 125 + 9*\/ 193 // \ 3*\/ 125 + 9*\/ 193 \ 3*\/ 125 + 9*\/ 193 // \ 3*\/ 125 + 9*\/ 193 /
=
9
9
x1 = 1.33040121988528 + 1.9102617040202*i
x2 = 1.33040121988528 - 1.9102617040202*i
x3 = -1.66080243977055
x4 = -1.0
x4 = -1.0