A-LevelMathematicsAlgebra9709/12 · Oct/Nov 2010 · Q14 Marks
Find the first 3 terms in the expansion, in ascending powers of x, of (1 – 2x²)⁸.
- (i)Find the first 3 terms in the expansion, in ascending powers of x, of (1 – 2x²)⁸.[2]
- (ii)Find the coefficient of x⁴ in the expansion of (2 – x²)(1 – 2x²)⁸.[2]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2010). The mark or mark type is shown in brackets.
- [B2, 1] 1+8(-2x²) + 8C2(-2x²)²
- Loses 1 for each error
- 1-16x² + 112x⁴
- [M1] (2 – x²) × their (1 – 16x² + 112x⁴)
- Must consider exactly 2 terms
- (2 × their 112) – their (−16)
- [A1√] 240
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