Calculus (3rd Edition)

Published by W. H. Freeman
ISBN 10: 1464125260
ISBN 13: 978-1-46412-526-3

Chapter 3 - Differentiation - 3.1 Definition of the Derivative - Exercises - Page 102: 9

Answer

See explanation

Work Step by Step

The slope of the secant line is: $$\frac{f(2.5)-f(2)}{2.5-2}=\frac{2.5-2}{2.5-2}=1$$ The equation of the tangent line to the graph of $f$ at $x=2$ is: $$y=f(2)+f'(2)(x-2)$$ where $f'(2)$ is the slope of the line. Since the red line is the tangent line to the graph of $f$ at $x=2$ it follows that $f'(2)$ is its slope. Notice as the tilt of the line is large as the slope is larger too. The slope of the secant line is greater than the slope $f'(2)$ of the tangent line (red line) to $f$ because the tilt of the secant line is greater than the tilt of the red line.
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