Calculus: Early Transcendentals 8th Edition

Published by Cengage Learning
ISBN 10: 1285741552
ISBN 13: 978-1-28574-155-0

Chapter 1 - Section 1.2 - Mathematical Models: A Catalog of Essential Functions. - 1.2 Exercises - Page 36: 29

Answer

The light is 4 times brighter.

Work Step by Step

Let the initial distance from the lamp be $2d$. $f(2d)=k(2d)^{-2}=\frac{k}{4d^{2}}$ Final distance = d. $f(d)=kd^{-2}=4\times\frac{k}{4d^{2}}$ $\therefore$ The light is 4 times brighter.
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