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Binomial Expansion

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Question 86

In this question you should assume −13<x<13\displaystyle -\frac{1}{3} < x < \frac{1}{3}−31​<x<31​

You may use

(1−3x)−2=1+6x+27x2+108x3+… (1-3x)^{-2}=1+6x+27x^2+108x^3+\dots (1−3x)−2=1+6x+27x2+108x3+…

and

1+3x+9x2+27x3+⋯=11−3x 1+3x+9x^2+27x^3+\dots=\frac{1}{1-3x} 1+3x+9x2+27x3+⋯=1−3x1​

Hence or otherwise find and simplify an expression for 2+9x+36x2+135x3+…2 + 9x + 36x^2 + 135x^3 + \dots2+9x+36x2+135x3+…

[3]
Markscheme

Binomial Expansion Questions

  1. A Level
  2. /Maths
  3. /Binomial Expansion

408 exam-style questions on Edexcel A Level Maths Binomial Expansion, covering 4.1 Expanding (1 + x)^n, 4.2 Expanding (a + bx)^n, and 4.3 Using Partial Fractions. Each one has a worked solution and a mark scheme showing where the marks go.

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