The cubic equation x³ +2x+1 = 0 has roots α, β, γ.
- (a)Find a cubic equation whose roots are α³ – 1, β³ – 1, γ³ – 1.[3]
- (b)Find the value of (α³ − 1)² + (β³ − 1)² + (γ³ − 1)². [2]
- (c)Find the value of (α³ − 1)³ + (β³ − 1)³ + (γ³ – 1)³.[2]
Mark scheme
Marking points from the official mark scheme (May/June 2025). The mark or mark type is shown in brackets.
- [B1] Uses correct substitution.
- [M1] Substitutes and obtains an equation not involving radicals.
- [A1] y³ + 6y² + 20y + 16 = 0
- [M1] Uses Σα² = (Σα)² - 2Σαβ.
- [A1] -4
- [M1] Uses their equation from (a) or a valid formula for the sum of cubes.
- [A1] 96
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