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Algebraic Methods

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Question 142
a.

Given that a a\,a and b b\,b are non-zero and that

9ab+4ba≥12 \frac{9a}{b} + \frac{4b}{a} \geq 12 b9a​+a4b​≥12

prove that a a\,a and b b\,b are either both positive or both negative.

[4]
b.

Prove, by counter example, that the inequality is not true for all values of a a\,a and bbb.

[2]
Markscheme

Algebraic Methods Questions

  1. A Level
  2. /Maths
  3. /Algebraic Methods

257 exam-style questions on Edexcel A Level Maths Algebraic Methods, covering 7.1 Algebraic Fractions, 7.2 Dividing Polynomials, 7.3 The Factor Theorem, 7.4 Mathematical Proof, and 7.5 Methods of Proof. Each one has a worked solution and a mark scheme showing where the marks go.

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