A-LevelMathematicsAlgebra9709/12 · Oct/Nov 2023 · Q14 Marks
The coefficient of x³ in the expansion of (3 + 2ax)⁵ is six times the coefficient of x² in the expansion of (2 + ax)⁶. Find the value of the constant a.
- The coefficient of x³ in the expansion of (3 + 2ax)⁵ is six times the coefficient of x² in the expansion of (2 + ax)⁶. Find the value of the constant a.[4]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2023). The mark or mark type is shown in brackets.
- [B1] May be seen in an expansion or with x³.
- [B1] May be seen in an expansion or with x².
- [M1] OE Equating their coefficient of x³ and 6 × their coefficient of x².
- [A1] Condone extra solution a = 0.
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