Elementary Geometry for College Students (5th Edition)

Given M(2.1,-5.7) is the mid point of $\overline{AB}$, Ponit A (1.7, 2.3) To find out the coordinates of point B(x2,y2) use theorem 10.1.2 Midpoint M(xm,ym) =($\frac{x1+x2}{2}$ , $\frac{y1+y2}{2}$) (2.1,-5.7) =($\frac{1.7+x2}{2}$ , $\frac{2.3+y2}{2}$) 2.1 =$\frac{1.7+x2}{2}$ ,-5.7 =$\frac{2.3+y2}{2}$ x2=4.2-1.7, y2 = -11.4-2.3 x2 = 2.5 , y2 = -13.7