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1.4 A: Proof

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Question 60

Detailed reasoning must be shown in this question.

A researcher studying fluid dynamics determines that for any two positive flow rates uuu and vvv in a bifurcated pipe, the 'effective velocity' VeV_eVe​ and the 'total sum' SSS are defined as:

Ve=u3+v3u2+v2andS=u+v V_e = \frac{u^3 + v^3}{u^2 + v^2} \quad \text{and} \quad S = u + v Ve​=u2+v2u3+v3​andS=u+v
a.

Use proof by contradiction to show that Ve<SV_e < SVe​<S for all positive real numbers uuu and vvv.

[4]
b.

By providing a counter-example, show that the statement in part (a) is not true for all real numbers uuu and vvv where u2+v2≠0u^2 + v^2 \neq 0u2+v2=0.

[2]

1.4 A: Proof Questions

  1. A Level
  2. /Maths
  3. /1.4 A: Proof

Practise AQA A Level Maths 1.4 A: Proof with exam-style questions for A Level Maths. 107 questions covering 1.4.1 Structure and methods of proof, matched to the AQA A Level Maths (7357) 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.

Question bank

1.4 A: Proof
1.5 B: Algebra and functions
1.6 C: Coordinate geometry in the (x, y) plane
1.7 D: Sequences and series
1.8 E: Trigonometry
1.9 F: Exponentials and logarithms
1.10 G: Differentiation
1.11 H: Integration
1.12 I: Numerical methods (A-level only)
1.13 J: Vectors