<p>If \(f(x) = |x|\) then \(f'(x) = \frac{|x|}{x}, x \neq 0\).</p><p><em>State whether this statement is true or false.</em></p>
Step-by-Step Solution
Key Concept: The derivative of |x| is actually sign(x) = x/|x| for x ≠ 0, not |x|/x. These expressions are reciprocals of each other, making the given statement false.
Step 1: Determine the derivative of $f(x) = |x|$ for $x \neq 0$.
The function $f(x) = |x|$ can be defined piecewise as:
$$f(x) = \begin{cases} x & \text{if } x > 0 \\ -x & \text{if } x < 0 \end{cases}$$
For $x > 0$, $f(x) = x$, so its derivative is $f'(x) = \frac{d}{dx}(x) = 1$.
For $x < 0$, $f(x) = -x$, so its derivative is $f'(x) = \frac{d}{dx}(-x) = -1$.
Thus, the derivative of $f(x) = |x|$ for $x \neq 0$ is:
$$f'(x) = \begin{cases} 1 & \text{if } x > 0 \\ -1 & \text{if } x < 0 \end{cases}$$
Step 2: Evaluate the expression $\frac{|x|}{x}$ for $x \neq 0$.
Consider the expression $\frac{|x|}{x}$:
For $x > 0$, $|x| = x$, so $\frac{|x|}{x} = \frac{x}{x} = 1$.
For $x < 0$, $|x| = -x$, so $\frac{|x|}{x} = \frac{-x}{x} = -1$.
Thus, the expression $\frac{|x|}{x}$ for $x \neq 0$ is:
$$\frac{|x|}{x} = \begin{cases} 1 & \text{if } x > 0 \\ -1 & \text{if } x < 0 \end{cases}$$
Step 3: Compare the results.
From Step 1, $f'(x) = 1$ for $x > 0$ and $f'(x) = -1$ for $x < 0$.
From Step 2, $\frac{|x|}{x} = 1$ for $x > 0$ and $\frac{|x|}{x} = -1$ for $x < 0$.
Since the expressions for $f'(x)$ and $\frac{|x|}{x}$ are identical for all $x \neq 0$, the statement is true.
Correct Answer: A