Given the equation z3=8 Because equation degree is equal to = 3 - does not contain even numbers in the numerator, then the equation has single real root. Get the root 3-th degree of the equation sides: We get: 3z3=38 or z=2 We get the answer: z = 2
All other 2 root(s) is the complex numbers. do replacement: w=z then the equation will be the: w3=8 Any complex number can presented so: w=reip substitute to the equation r3e3ip=8 where r=2 - the magnitude of the complex number Substitute r: e3ip=1 Using Euler’s formula, we find roots for p isin(3p)+cos(3p)=1 so cos(3p)=1 and sin(3p)=0 then p=32πN where N=0,1,2,3,... Looping through the values of N and substituting p into the formula for w Consequently, the solution will be for w: w1=2 w2=−1−3i w3=−1+3i do backward replacement w=z z=w
The final answer: z1=2 z2=−1−3i z3=−1+3i
Vieta's Theorem
it is reduced cubic equation pz2+qz+v+z3=0 where p=ab p=0 q=ac q=0 v=ad v=−8 Vieta Formulas z1+z2+z3=−p z1z2+z1z3+z2z3=q z1z2z3=v z1+z2+z3=0 z1z2+z1z3+z2z3=0 z1z2z3=−8