Big Ideas Math - Algebra 1, A Common Core Curriculum

Published by Big Ideas Learning LLC
ISBN 10: 978-1-60840-838-2
ISBN 13: 978-1-60840-838-2

Chapter 1 - Solving Linear Equations - 1.4 - Solving Absolute Value Equations - Exercises - Page 33: 51

Answer

No solution : $|x - 2| + 6 = 0$ $|x - 6| - 5 = -9$ One solution: $|x - 1| + 4 = 4$ $|x - 5| - 8 = -8$ Two solutions : $|x + 3| - 1 = 0$ $|x + 8| + 2 = 7$

Work Step by Step

Let's consider the absolute value equation $$|x-h|=d.\tag{1}$$ $\textbf{Case 1: No solution}$ The equation $(1)$ cannot be solved if the right hand side is a negative number ($d<0$) as absolute values are always positive. a) $|x - 2| + 6 = 0$ Subtract $6$ from both sides $$|x - 2| = -6.$$ As RHS is negative, the equation has no solution. b) $|x - 6| - 5 = -9$ Add $5$ to both sides $$|x-6| = -4$$ As $RHS$ is negative, the equation has no solution. $\textbf{Case 2: One solution}$ The equation $(1)$ will have one solution if the right hand side is $0$ as zero cannot assume any sign ($d=0$). a) $|x - 1| + 4 = 4$ Subtract $4$ from both sides $$|x-1| = 0.$$ As $RHS = 0$, we have one solution. b) $|x - 5| - 8 = -8$ Add $8$ to both sides $$|x - 5| = 0.$$ As $RHS = 0$, the equation has one solution. $\textbf{Case 3: Two solutions}$ If the right hand side of the solution is a real number greater than $0$ ($d>0$), then it has $2$ solutions. a) $|x + 3| - 1 = 0$ Add $1$ to both sides $$|x+3| = 1.$$ As $RHS =1 >0$, there are $2$ solutions. b) $|x + 8| + 2 = 7$ Subtract $2$ from both sides $$|x+8| = 5.$$ As $RHS = 5 >0$, this equation has $2$ solutions.
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