A-LevelMathematicsSeries9709/31 · May/June 2017 · Q24 Marks
Expand 1/√(1 + 6x) in ascending powers of x, up to and including the term in x³, simplifying the coefficients.
Mark scheme
Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.
- EITHER: State a correct unsimplified version of the x or x² or x³ term in the expansion of (1+6x)^(-1/2) (M1
- State correct first two terms 1-3x A1
- Obtain term +27/2 x² A1
- Obtain term -135/2 x³ in final answer A1)
- OR: Differentiate expression and evaluate f(0) and f'(0), where f'(x) = k(1+6x)^(-3/2) (M1
- Obtain correct first two terms 1-3x A1
- Obtain term +27/2 x² A1
- Obtain term -135/2 x³ in final answer A1)
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