The coordinates of point D is (-2,-6)
Given :
the point (2,1) is the midpoint of CD. Point C has coordinates (6,8).
Let coordinates of point D is (x2,y2)
C is (6,8) that is (x1,y1)
Lets apply midpoint formula
[tex](\frac{x_1+x_2}{2},\frac{y_1+y_2}{2} )\\[/tex]
Plug in x1 and y1 values inside the formula and make is equal to (2,1)
[tex](\frac{6+x_2}{2},\frac{8+y_2}{2} )=(2,1)\\\\\frac{6+x_2}{2}=2\\6+x_2=4\\x_2=4-6=-2\\x_2=-2\\\\\\\frac{8+y_2}{2} =1\\8+y_2=2\\y_2=2-8\\y_2=-6[/tex]
so coordinates of point D is (-2,-6)
Learn more : brainly.com/question/11748965
