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z^3=8

z^3=8 equation

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Numerical solution:

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The solution

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 3    
z  = 8
z3=8z^{3} = 8
Detail solution
Given the equation
z3=8z^{3} = 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:
z33=83\sqrt[3]{z^{3}} = \sqrt[3]{8}
or
z=2z = 2
We get the answer: z = 2

All other 2 root(s) is the complex numbers.
do replacement:
w=zw = z
then the equation will be the:
w3=8w^{3} = 8
Any complex number can presented so:
w=reipw = r e^{i p}
substitute to the equation
r3e3ip=8r^{3} e^{3 i p} = 8
where
r=2r = 2
- the magnitude of the complex number
Substitute r:
e3ip=1e^{3 i p} = 1
Using Euler’s formula, we find roots for p
isin(3p)+cos(3p)=1i \sin{\left(3 p \right)} + \cos{\left(3 p \right)} = 1
so
cos(3p)=1\cos{\left(3 p \right)} = 1
and
sin(3p)=0\sin{\left(3 p \right)} = 0
then
p=2πN3p = \frac{2 \pi N}{3}
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=2w_{1} = 2
w2=13iw_{2} = -1 - \sqrt{3} i
w3=1+3iw_{3} = -1 + \sqrt{3} i
do backward replacement
w=zw = z
z=wz = w

The final answer:
z1=2z_{1} = 2
z2=13iz_{2} = -1 - \sqrt{3} i
z3=1+3iz_{3} = -1 + \sqrt{3} i
Vieta's Theorem
it is reduced cubic equation
pz2+qz+v+z3=0p z^{2} + q z + v + z^{3} = 0
where
p=bap = \frac{b}{a}
p=0p = 0
q=caq = \frac{c}{a}
q=0q = 0
v=dav = \frac{d}{a}
v=8v = -8
Vieta Formulas
z1+z2+z3=pz_{1} + z_{2} + z_{3} = - p
z1z2+z1z3+z2z3=qz_{1} z_{2} + z_{1} z_{3} + z_{2} z_{3} = q
z1z2z3=vz_{1} z_{2} z_{3} = v
z1+z2+z3=0z_{1} + z_{2} + z_{3} = 0
z1z2+z1z3+z2z3=0z_{1} z_{2} + z_{1} z_{3} + z_{2} z_{3} = 0
z1z2z3=8z_{1} z_{2} z_{3} = -8
The graph
-10.0-7.5-5.0-2.50.02.55.07.510.012.515.017.5-25002500
Rapid solution [src]
z1 = 2
z1=2z_{1} = 2
              ___
z2 = -1 - I*\/ 3 
z2=13iz_{2} = -1 - \sqrt{3} i
              ___
z3 = -1 + I*\/ 3 
z3=1+3iz_{3} = -1 + \sqrt{3} i
z3 = -1 + sqrt(3)*i
Sum and product of roots [src]
sum
             ___            ___
2 + -1 - I*\/ 3  + -1 + I*\/ 3 
(2+(13i))+(1+3i)\left(2 + \left(-1 - \sqrt{3} i\right)\right) + \left(-1 + \sqrt{3} i\right)
=
0
00
product
  /         ___\ /         ___\
2*\-1 - I*\/ 3 /*\-1 + I*\/ 3 /
2(13i)(1+3i)2 \left(-1 - \sqrt{3} i\right) \left(-1 + \sqrt{3} i\right)
=
8
88
8
Numerical answer [src]
z1 = 2.0
z2 = -1.0 - 1.73205080756888*i
z3 = -1.0 + 1.73205080756888*i
z3 = -1.0 + 1.73205080756888*i
The graph
z^3=8 equation