Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 1 - Section 1.9 - The Coordinate Plane; Graphs of Equations; Circles - 1.9 Exercises - Page 102: 20

Answer

See the images below.

Work Step by Step

(a) $|x|\leq 1$ has two possible solution, due to the reason, that the value of $x$ can be either positive or negative (In case of $0$ it doesn't affect anything). So we have to solve $2$ possible inequalities: $x\leq 1$ or $-x\leq 1$ $x\leq 1$ $x\geq -1$ The value of $x$ varies between $-1$ and $1$, so the region of solution is closed interval between lines $x=-1$ and $x=1$ (Blue Region). See the image above. $|y|\leq 3$ Can be solved using the same method used above. $y\leq 3$ or $-y\leq 3$ We have: $y\leq 3$ $y\geq -3$ The solution lies between $y=3$ and $y=-3$ lines of closed interval (Green Region). See the image above. (b) For the inequality ($xy>0$) to be true, both $x$ and $y$ have to be either positive or negative. Which means, that we need regions, where both $x$ and $y$ are either positive or negative at the same time. These regions are $1^{st}$ and $3^{rd}$ quadrants. See the image below.
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