1977 AMC 12 Question 5
AMC12 · 1977 AMC 12
The set of all points $P$ such that the sum of the (undirected) distances from $P$ to two fixed points $A$ and $B$ equals the distance between $A$ and $B$ is
the line segment from $A$ to $B$
the line passing through $A$ and $B$
the perpendicular bisector of the line segment from $A$ to
$B$
an ellipse having positive area
a parabola