Intermediate Algebra (6th Edition)

Published by Pearson
ISBN 10: 0321785045
ISBN 13: 978-0-32178-504-6

Chapter 9 - Section 9.8 - Exponential and Logarithmic Equations and Problem Solving - Exercise Set - Page 590: 17

Answer

The solutions are $x=-2$ and $x=3$.

Work Step by Step

RECALL: $\log_a{b}=x \longrightarrow a^x=b$ where $b\gt0$ Use this rule in converting the equation to its equivalent exponential equation to have: $6^1=x^2-x \\6=x^2-x$ Subtract 6 to both sides to have: $0=x^2-x-6 \\x^2-x-6=0$ Factor the trinomial to have: $(x-3)(x+2)=0$ Equate each factor to zero then solve each equation to have: $x-3=0 \text{ or } x+2 = 0 x=3 \text{ or } x=-2$ Note that in $\log_a{b}$, the value of $b$ has to be positive. This means that in $\log_6{(x^2-x)}$, the value of $x^2-x$ must be positive. Check if both solutions are valid to have: For x = 3: $x^2-x = 3^2 - 3 = 9-3=6$ For x=-2: $x^2-x = (-2)^2 -(-2) = 4+2 = 6$ Since both solutions make $x^2-x$ positive, then both are valid. Therefore, the solutions to the given equation are $-2$ and $3$.
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