A-LevelMathematicsSeries9709/12 · Oct/Nov 2016 · Q46 Marks
In the expansion of (3 – 2x) (1 + x/2)^n, the coefficient of x is 7. Find the value of the constant n and hence find the coefficient of x².
- In the expansion of (3 – 2x) (1 + x/2)^n, the coefficient of x is 7. Find the value of the constant n and hence find the coefficient of x².[6]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2016). The mark or mark type is shown in brackets.
- [B1] Term in x = nx/2 Could be implied by use of a numerical n.
- [M1] (Their 2 terms in x) = 7
- [A1] → n=6
- [B1] Term in x² = n(n-1)/2 (x/2)² May be implied by (their n) × (their n-1) ÷ 8.
- [M1] Considers 2 terms in x².
- [A1] aef
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