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 10 - Radical Functions and Equations - 10.3 - Solving Radical Equations - Exercises - Page 566: 81

Answer

No

Work Step by Step

No, because if $2x+5$ is negative, then $\sqrt{(2x+5)^2}$ will be $-(2x+5)$. The given equation can be written: $$|2x+5|=2x+5.$$ For $x\geq -\frac{5}{2}$ the equation becomes: $$2x+5=2x+5$$ which is true for any $x\geq -\frac{5}{2}$, while for $x<-\frac{5}{2}$ the equation can be written: $$-2x-5=2x+5$$ which is true only for $x=-\frac{5}{2}$. Your friend is not correct.
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