Consider the polynomials:
R(x) = x⁶ – x⁵ – x³ – x² - x and:
S(x) = x⁴ – x³ – x² - 1
z₁, z₂, z₃, and z₄ are roots of S(x) = 0
Determine R(z₁) + R(z₂) + R(z₃) + R(z₄).