Calculus: Early Transcendentals 8th Edition

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

Chapter 1 - Problems - Page 76: 13

Answer

$$[-1,1-\sqrt3)\cup(1+\sqrt3,3]$$

Work Step by Step

$$\ln{(x^{2}-2x-2)}\leq0\\ e^{\ln{(x^{2}-2x-2)}}\leq e^0\\ x^{2}-2x-2\leq1\\ x^{2}-2x-3\leq0\\ (x-3)(x+1)\leq0\\ x\leq3\qquad x\geq-1\\ [-1,3]$$ $$\mbox{Also, }x^{2}-2x-2\gt0\mbox{, as }\ln\mbox{ can only be taken of a positive number.}\\ x^{2}-2x-2\gt0\\ (x-(1+\sqrt 3))(x-(1-\sqrt 3))\gt0\\ (x-1-\sqrt 3)(x-1+\sqrt 3)\gt0\\ x\gt1+\sqrt3\qquad x\lt1-\sqrt3\\ (-\infty,1-\sqrt3)\cup(1+\sqrt3,\infty)$$ $$\mbox{Therefore, the solution is }[-1,1-\sqrt3)\cup(1+\sqrt3,3]$$
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