| Exam Board | WJEC |
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| Module | Unit 3 (Unit 3) |
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| Session | Specimen |
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| Topic | Proof |
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15. Prove by contradiction the following proposition.
When \(x\) is real and positive,
$$4 x + \frac { 9 } { x } \geq 12$$
The first line of the proof is given below.
Assume that there is a positive and a real value of \(x\) such that
$$4 x + \frac { 9 } { x } < 12$$