A-LevelMathematicsSeries9709/32 · Feb/Mar 2024 · Q25 Marks
Find the coefficient of x² in the expansion of (2x - 5)√4-x.
- (a)Find the coefficient of x² in the expansion of (2x - 5)√4-x.[4]
- (b)State the set of values of x for which the expansion in part (a) is valid.[1]
Mark scheme
Marking points from the official mark scheme (Feb/Mar 2024). The mark or mark type is shown in brackets.
- [B1] State unsimplified term in x, or its coefficient, in the expansion of (4-x)½
- [B1] State unsimplifed term in x², or its coefficient, in the expansion of (4-x)½
- [M1] Multiply by (2x-5) and obtain 2 terms in x², allow even if errors in 4², signs, etc.
- [A1] Obtain 27/64 or -0.421875 or -54/128
- [B1] |x|<4 or -4 < x <4.
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