The absolute value function

Indicate the domain and the image of the following function: $h(x)=|3x|$

In this case the function is equivalent to: $$|3x|=\left\{\begin{array}{rcl} 3x & \mbox{ if } & 3x\geq0 \\ -3x & \mbox{ if } & 3x < 0 \end{array}\right.$$ And this is equivalent to: $$|x|=\left\{\begin{array}{rcl} 3x & \mbox{ if } & x\geq0 \\ -3x & \mbox{ if } & x < 0 \end{array}\right.$$

Therefore $Dom (f) =\mathbb{R}$ and $Im (f) = [0, +\infty)$.

$Dom (f) =\mathbb{R}$, $Im (f) = [0, +\infty)$

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