Introductory Algebra for College Students (7th Edition)

Published by Pearson
ISBN 10: 0-13417-805-X
ISBN 13: 978-0-13417-805-9

Chapter 1 - Section 1.8 - Exponents and Order of Operations - Exercise Set - Page 102: 110

Answer

False The true statement should be: "If $x$ is $3$, then the value of $-3x - 9$ is $-18$."

Work Step by Step

To find out if this statement is true or false, we want to substitute $-3$ for $x$: $$-3(-3) - 9 = -18$$ Multiply first, according to order of operations: $$9 - 9 = -18$$ Subtract: $$0 = -18$$ We see that the two sides of the equation are not equal; therefore, this statement is false. In order to make this statement true, we can substitute $3$ for $x$: $$-3(3) - 9 = -18$$ Let's check. Multiply first, according to order of operations: $$-9 - 9 = -18$$ Let's subtract: $$-18 = -18$$ When we substitute $3$ in for $x$, the two sides of the equation; therefore, $3$ is a solution of the equation, not $-3$.
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