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1.7 D: Sequences and series

1.7 D: Sequences and series

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Question 149

Given that kkk is a constant and the binomial expansion of

1+kx,∣kx∣<1 \sqrt{1 + kx}, \quad |kx| < 1 1+kx​,∣kx∣<1

in ascending powers of xxx up to the term in x3x^3x3 is

1+14x+Ax2+Bx3 1 + \frac{1}{4}x + Ax^2 + Bx^3 1+41​x+Ax2+Bx3
a.

(i) find the value of kkk,

(ii) find the value of the constant AAA and the constant BBB.

[5]
b.

Use the expansion to find an approximate value to 1.2\sqrt{1.2}1.2​.

Show your working and give your answer to 6 decimal places.

[4]
Markscheme

1.7 D: Sequences and series Questions

  1. A Level
  2. /Maths
  3. /1.7 D: Sequences and series

308 exam-style questions on AQA A Level Maths 1.7 D: Sequences and series, covering 1.7.1 Binomial expansion, 1.7.2 Types of sequence (A-level only), 1.7.3 Sigma notation (A-level only), 1.7.4 Arithmetic sequences and series (A-level only), 1.7.5 Geometric sequences and series (A-level only), and 1.7.6 Sequences and series in modelling (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.

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