Chapter 1 - Tools of Geometry - 1-8 Perimeter, Circumference, and Area - Practice and Problem-Solving Exercises - Page 67: 64

a) 8.5 b) (5.5,5)

a) Use the distance formula: $d=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}$ $d=\sqrt{(7-4)^2+(9-1)^2}$ $d=\sqrt{(3)^2+(8)^2}$ $d=\sqrt{9+64}$ $d=\sqrt{73}$ $d=8.5$ b) Use the midpoint formula: $M_x=\frac{x_1+x_2}{2}=\frac{4+7}{2}=\frac{11}{2}=5.5$ $M_y=\frac{y_1+y_2}{2}=\frac{1+9}{2}=\frac{10}{2}=5$