## Precalculus (6th Edition)

Option (D); $x=\left\{\frac{1}{3}, 7\right\}$
RECALL: The zero-factor property states that if $ab=0$, then either $a=0$ or $b=0$ or both are zero. Among the given equation, the one in Option (D) is set up for direct use of the zero-factor property. Using the property gives: \begin{array}{ccc} &3x-1=0 &\text{or} &x-7=0 \\&3x=1 &\text{or} &x=7 \\&x=\frac{1}{3} &\text{or} &x=7 \end{array} Thus, $x=\left\{\frac{1}{3}, 7\right\}$.