A3. A line segment has one endpoint at the point $(-2,1)$. The midpoint of the segment is at the point $(0,-1)$. In which point is the other endpoint?
(A) $(2,-3)$
(B) $(-1,0)$
(C) $(1,-1)$
(D) $(2,3)$
(E) None of the above.
A3. From the midpoint formula for a line segment, we set up the equations: $0=\frac{-2+x_{2}}{2}$ and $-1=\frac{1+y_{2}}{2}$. From the first, we get $x_{2}=2$, and from the second, $y_{2}=-3$. The second endpoint is at the point $(2,-3)$.