The function $f(x) = |x|$ can be expressed piecewise as:
A$f(x) = x$ for all $x$
B$f(x) = x$ if $x \ge 0$; $f(x) = -x$ if $x < 0$
C$f(x) = -x$ for all $x$
D$f(x) = x^{2}$
Answer & Solution
Correct answer: B. $f(x) = x$ if $x \ge 0$; $f(x) = -x$ if $x < 0$
The modulus function returns the non-negative part. For $x \ge 0$, $|x| = x$. For $x < 0$, $|x| = -x$ (flipping the sign makes it positive).
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