Answer
$m_1=m_2$;
$y$-intercepts;
$m_1 \cdot m_2=-1$
Work Step by Step
Two lines are parallel if their slopes are equal, i.e., $m_1=m_2$, and their $y$-intercepts are not equal (so they are not the same line).
Two lines are perpendicular if $m_1 \cdot m_2=-1$ or their slopes are negative reciprocals of each other.
