The coordinates of the midpoint if the endpoints are (x₁,y₁) and (x₂,y₂):
\((\frac{x_1+x_2}{2}, \frac{y_1+y_2}{2})\)
One endpoint is (3,5), the midpoint is (5,-11). The other endpoint is (x,y).
\(\frac{3+x}{2}=5 \ \ \ \ \ \ \ \ |\times 2 \\
3+x=10 \ \ \ \ \ |-3 \\
x=7 \\ \\
\frac{5+y}{2}=-11 \ \ \ \ \ |\times 2 \\
5+y=-22 \ \ \ |-5 \\
y=-27\)
The coordinates of endpoint M are (7,-27).
