Question

E is the midpoint of DF¯¯¯¯¯¯¯¯. What are the coordinates of F?

Segment DF with midpoint E. The coordinates of point E are 1, negative 1. The coordinates of point D are 10, 7.

Answer 1

`~~~~~~~~~~~~\textit{middle point of 2 points } \\\\ D(\stackrel{x_1}{10}~,~\stackrel{y_1}{7})\qquad F(\stackrel{x_2}{x}~,~\stackrel{y_2}{y}) \qquad \left(\cfrac{ x_2 + x_1}{2}~~~ ,~~~ \cfrac{ y_2 + y_1}{2} \right) \\\\\\ \left(\cfrac{ x +10}{2}~~~ ,~~~ \cfrac{ y +7}{2} \right) ~~ = ~~\stackrel{\textit{\LARGE E}}{(1~~,~~-1)} \\\\[-0.35em] ~\dotfill\\\\ \cfrac{ x +10}{2}=1\implies x+10=2\implies \boxed{x=-8} \\\\[-0.35em] ~\dotfill\\\\ \cfrac{ y +7}{2}=-1\implies y+7=-2\implies \boxed{y=-9}`