If z^2 + z + 1 = 0, that means that if we'll multiply both
sides by (z-1), we'll get:
(z-1)(z^2 + z + 1) =
0
But the product is the result of difference of
cubes:
z^3 - 1 = (z-1)(z^2 + z +
1)
If (z-1)(z^2 + z + 1) = 0, then z^3 - 1 =
0
We'll add 1 both sides:
z^3
= 1
z1 and z2 are the roots of the equation z^3 - 1 = 0,
so:
z1^3 = 1
z2^3 =
1
From the equation z^2 + z + 1 =
0
z + 1 = -z^2
We'll
substitute z1 and z2:
z1 + 1 =
-z1^2
z2 + 1 = -z2^2
(z1 +
1)^10 + (z2 + 1)^10 = (-z1^2)^10 + (-z2^2)^10
We'll
re-write the expression (-z1^2)^10 + (-z2^2)^10:
(-z1^2)^10
+ (-z2^2)^10 = (z1^2)^10 + (z2^2)^10
(z1^10)^2 +
(z2^10)^2
We'll write z1^10 =
z1^(9+1)
z1^(9+1)
= z1^9*z1
z1^9*z1 =
(z1^3)^2*z1
But z1^3 = 1
z1^10
= 1^2*z1
z1^10 = z1
z2^10 =
z2
So,
(z1^10)^2 + (z2^10)^2
= z1^2 + z2^2
We'll use Viete's relations to express z1 +
z2:
z1 + z2 = -b/a
where b and
a are the coefficients of the quadratic equation
az^2 + bz
+ c = 0
In our case, the quadratic
is:
z^2 +z +1 = 0
a =
1
b = 1
c =
1
z1 + z2 = -1/1
z1 + z2 =
-1
z1*z2 = c/a
z1*z2 =
1
z1^2 + z2^2 = (z1 + z2)^2 -
2z1*z2
(z1 + 1)^10 + (z2 + 1)^10 = (-1)^2 -
2*1
(z1 + 1)^10 + (z2 + 1)^10 = 1 -
2
(z1 + 1)^10 + (z2 + 1)^10 =
-1
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