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## 'Loch Ness' printed from http://nrich.maths.org/

Remember that the function $f(x) = |x|$ is defined as:

$$\eqalign{ y &= x \ {\rm for } \ x\geq 0 \cr &= -x \ {\rm
for } \ x < 0 .}$$

Split up the domain of the function.