Page 59 - Calculus Demystified

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Fig. 1.49 CHAPTER 1 Basics

Fig. 1.50

3
You Try It: Sketch f(x) = x + x and its inverse.
Another useful fact is this: Since an invertible function must be one-to-one, two
different x values cannot correspond to (that is, be “sent by the function to”) the
same y value. Looking at Figs. 1.51 and 1.52, we see that this means
In order for f to be invertible, no horizontal line can
intersect the graph of f more than once.

Fig. 1.51