The midpoint of the line segment between $(x,y)$ and $(-9,1)$ is $(3,-5)$. Find $(x,y)$.
To find the midpoint of a line segment, I need to average the x-coordinates and the y-coordinates of the endpoints. So, if the midpoint is $(3,-5)$, then I have $\frac{x+(-9)}{2}=3$ and $\frac{y+1}{2}=-5$. I can solve these equations for $x$ and $y$ by multiplying both sides by 2 and simplifying. For the first equation, I get $x-9=6$, so $x=15$. For the second equation, I get $y+1=-10$, so $y=-11$. Therefore, the other endpoint of the line segment is $(15,-11)$.

