of y = f ′(x).
Figure N3–6From the graphs above we can make the following observations:
(1) At the points where the slope of f (in Figure N3–5) equals 0, the graph of f
′ (Figure N3–6) has x-intercepts: approximately x = −1.8 and x = 1.1. We’ve
drawn horizontal broken lines at these points on the curve in Figure N3-5.
(2) On intervals where f , the derivative is . We see here that f
decreases for x < −1.8 (approximately) and for x > 1.1 (approximately), and that
f increases for −1.8 < x < 1.1 (approximately). In Chapter 4 we discuss other
behaviors of f that are reflected in the graph of f ′.