## Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

Using $y=mx+b$ where $m$ is the slope, the slope of the first equation, \begin{array}{l}\require{cancel} y=\dfrac{1}{3}x-7 \end{array} is $m_1= \dfrac{1}{3} .$ Using $y=mx+b$ where $m$ is the slope, the slope of the second equation, \begin{array}{l}\require{cancel} y+3x=1 \\\\ y=-3x+1 \end{array} is $m_2= -3 .$ Since $m_1\cdot m_2=-1,$ then the given lines are $\text{ perpendicular .}$