4.2 Expanding (a + bx)^n
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a.

Use the binomial expansion to expand

(9−4x)−12∣x∣<94(9 - 4x)^{-\frac{1}{2}} \quad |x| < \frac{9}{4}(9−4x)−21​∣x∣<49​

in ascending powers of xxx, up to and including the term in x2x^2x2, giving each coefficient as a fully simplified fraction.

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b.

f(x)=6+kx9−4xwhere k is a constant and ∣x∣<94f(x) = \frac{6 + kx}{\sqrt{9 - 4x}} \quad \text{where } k \text{ is a constant and } |x| < \frac{9}{4}f(x)=9−4x​6+kx​where k is a constant and ∣x∣<49​

Given that the series expansion of f(x)f(x)f(x), in ascending powers of xxx, is

2+49x+px2+…where p is a constant2 + \frac{4}{9}x + px^2 + \dots \quad \text{where } p \text{ is a constant}2+94​x+px2+…where p is a constant

find the value of kkk,

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c.

find the value of ppp.

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4.2 Expanding (a + bx)^n Questions

Practise Edexcel A Level Maths 4.2 Expanding (a + bx)^n with exam-style questions for A Level Maths. 99 questions, matched to the Edexcel A Level Maths (9MA0) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.

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4.2 Expanding (a + bx)^n Questions

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