JEE Mains · Maths · STD 12 - 1. relation and function
If \(f(x)=\frac{\left(\tan 1^{\circ}\right) x+\log _{\varepsilon}(123)}{x \log _{\varepsilon}(1234)-\left(\tan 1^{\circ}\right)}, x > 0\), then the least value of \(f(f(x))+f\left(f\left(\frac{4}{x}\right)\right)\) is \(...........\).
- A \(8\)
- B \(4\)
- C \(2\)
- D \(0\)
Answer & Solution
Correct Answer
(B) \(4\)
Step-by-step Solution
Detailed explanation
Let \(f(x)=\frac{A x+B}{C x-A}\) \(f(f(x))=\frac{A\left(\frac{A x+B}{C x-A}\right)+B}{C\left(\frac{A x+B}{C x-A}\right)-A}=x\) \(f\left(f\left(\frac{4}{x}\right)\right)=\frac{4}{x}f(f(x))+f\left(f\left(\frac{4}{x}\right)\right)=x+\frac{4}{x} \geq 4(b y A M . \geq G . M .)\)
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