A-LevelMathematicsSeries9709/12 · Oct/Nov 2009 · Q25 Marks
Find, in terms of the non-zero constant k, the first 4 terms in the expansion of (k + x)⁸ in ascending powers of x.
- (i)Find, in terms of the non-zero constant k, the first 4 terms in the expansion of (k + x)⁸ in ascending powers of x.[3]
- (ii)Given that the coefficients of x² and x³ in this expansion are equal, find the value of k.[2]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2009). The mark or mark type is shown in brackets.
- [3] k⁸ + 8k⁷x + 28k⁶x² + 56k⁵x³ (Loses 1 for each error)
- [1] 28k⁶ = 56k⁵ (M1)
- [1] k = 2 (A1)
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