## 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} x+y=5 \\\\ y=-x+5 \end{array} is $m_1= -1 .$ Using $y=mx+b$ where $m$ is the slope, the slope of the second equation, \begin{array}{l}\require{cancel} x-y=1 \\\\ -y=-x+1 \\\\ y=x-1 \end{array} is $m_2= 1 .$ Since $m_1\cdot m_2=-1,$ then the given lines are $\text{ perpendicular .}$