Find the first 3 terms in the expansion of (2x² - 1/(3x))⁵, in descending powers of x.
- (i)Find the first 3 terms in the expansion of (2x² - 1/(3x))⁵, in descending powers of x.[3]
- (ii)Hence find the coefficient of x⁷ in the expansion of (3 + 1/x³) (2x² - 1/(3x))⁵.[2]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2016). The mark or mark type is shown in brackets.
- [3] (i) 32x¹⁰ - 80/3 x⁷ + 80/9 x⁴ B1 for each term, powers of x must be simplified
- [1] (ii) Coefficients needed: (3 × their -80/3) + (1 × their 32) M1 for dealing with 2 terms
- [1] (ii) = -48 A1 Allow A1 for -48x⁷
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