O-LevelAdditional MathematicsSeries4037/12 · Oct/Nov 2019 · Q36 Marks
The first three terms in the expansion of (1-x/7)^14 (1-2x)^4 can be written as 1 + ax+bx². Find the value of each of the constants a and b.
- The first three terms in the expansion of (1-x/7)^14 (1-2x)^4 can be written as 1 + ax+bx². Find the value of each of the constants a and b.[6]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2019). The mark or mark type is shown in brackets.
- [2] B2 (1 - x/7)^14 = 1 - 2x + 13/7 x² All terms correct or B1 for 2 correct terms
- [2] B2 (1 - 2x)^4 = 1 - 8x + 24x² ... First three terms correct or B1 for one incorrect term
- [1] M1 For attempt to multiply out to obtain (1)-10x+mx², m≠16
- [1] A1 a = -10, b = 293/7 For both, need to identify a and b
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