The cubic equation 2x³ + 5x² - 6 = 0 has roots α, β, γ.
- (a)Find a cubic equation whose roots are 1/(α³), 1/(β³), 1/(γ³).[3]
- (b)Find the value of 1/(α⁶) + 1/(β⁶) + 1/(γ⁶).[3]
- (c)Find also the value of 1/(α⁹) + 1/(β⁹) + 1/(γ⁹).[2]
Mark scheme
Marking points from the official mark scheme (May/June 2022). The mark or mark type is shown in brackets.
- [B1] Substitutes.
- [M1] Cubes to eliminate radical.
- [A1]
- [B1 FT] Using their answer to part (a).
- [M1]
- [A1]
- [M1] Using their 216a⁻⁹ – 216a⁻⁶ – 53a⁻³ – 8 = 0
- [A1]
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