MCQ
Choose the correct answers:
Let $\text{f(x)}=\sqrt{1+\text{x}^2}$ then.
  • A
    $\text{f(xy)} = \text{f(x)}.\text{f(y)}$
  • B
    $\text{f(xy)} \geq \text{f(x)}.\text{f(y)}$
  • C
    $\text{f(xy)} \leq \text{f(x)}.\text{f(y)}$
  • D
    None of these

Answer

  1. $\text{f(xy)} \leq \text{f(x)}.\text{f(y)}$

Solution:

Given that: $\text{f(x)}=\sqrt{1+\text{x}^2}$

$\Rightarrow\text{f(xy)}=\sqrt{1+\text{x}^2\text{y}^2}$

and $\text{f(x)}.\text{f(y)}=\sqrt{1+\text{x}^2}.\sqrt{1+\text{x}^2}=\sqrt{1+\text{x}^2 +\text{y}^2+\text{x}^2\text{y}^2}$

$\therefore\sqrt{1+\text{x}^2\text{y}^2}\leq\sqrt{1+\text{x}^2 +\text{y}^2+\text{x}^2\text{y}^2}$

$\text{f(xy)} \leq \text{f(x)}.\text{f(y)}$

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