Algebra 1: Common Core (15th Edition)

Published by Prentice Hall
ISBN 10: 0133281140
ISBN 13: 978-0-13328-114-9

Chapter 1 - Foundations for Algebra - 1-8 An Introduction to Equations - Practice and Problem-Solving Exercises: 58

Answer

$y=-5$

Work Step by Step

In order to solve this algebraic expression, we must isolate the variable. A variable is the letter in the problem (for instance, in the equation x+2=10, x is the variable). Because addition and subtraction are inverse operations (they cancel each other out), we know we must add when a number is being subtracted from the variable and subtract when a number is being added to the variable. In the equation 9=4+(-y), we must get rid of the 4, which is on the same side as y, in order to solve. Thus, we subtract 4 on both sides of the equation to find that -y=5. We need y to be positive, so we divide by -1 on both sides of the equation to get that $y=-5$.
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