Answer
$m_1=m_2$;
y-intercepts;
$m_1 \cdot m_2=-1$
Work Step by Step
RECALL:
(1) Parallel lines have equal slopes but have different y-intercepts
(2) Perpendicular lines have slopes whose product is $-1$
Thus, the missing expressions in the given statements are (in order):
$m_1=m_2$;
y-intercepts;
$m_1 \cdot m_2=-1$
