Calculus, 10th Edition (Anton)

Published by Wiley
ISBN 10: 0-47064-772-8
ISBN 13: 978-0-47064-772-1

Chapter 11 - Three-Dimensional Space; Vectors - 11.1 Rectangular Coordinates In 3-Space; Spheres; Cylindrical Surfaces - Exercises Set 11.1 - Page 772: 49

Answer

Inequalities represent the set of all points in a 3 -space that are out of the cylinder $16=(-2+z)^{2}+(3+y)^{2}$

Work Step by Step

We complete squares in the given inequality \[ \begin{aligned} 6 y-4 z+z^{2}+y^{2}>3 & \Rightarrow\left(-4 z+z^{2}+4\right)+\left(6 y+y^{2}+9\right)>3+9+4 \\ & \Rightarrow(-2+z)^{2}+(3+y)^{2}>16 \end{aligned} \] Notice that \[ 16=(-2+z)^{2}+(3+y)^{2} \] It's a cylinder whose projection is at the level $yz$ in which the circle \[ 16=(-2+z)^{2}+(3+y)^{2} \] is centered at (0,-3,2) of radius $4=r $. And therefore the inequality represents the set of all points in 3 -space that are out of the cylinder $16=(-2+z)^{2}+(3+y)^{2}$
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