A-LevelMathematicsSeries9709/12 · Oct/Nov 2019 · Q14 Marks
The coefficient of x² in the expansion of (4 + ax)(1 + x/2)^6 is 3. Find the value of the constant a.
- The coefficient of x² in the expansion of (4 + ax)(1 + x/2)^6 is 3. Find the value of the constant a.[4]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2019). The mark or mark type is shown in brackets.
- [B1 B1] 6x/2, 15x^2/4 OE In or from a correct expansion. Can be implied by correct equation.
- [M1] x^2(4 + ax) → 3a + 15 = 3 2 terms in x² equated to 3 or 3x². Condone x² on one side only.
- [A1] a = -4 CAO
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