Chapter 1 - Tools of Geometry - 1-7 Midpoint and Distance in the Coordinate Plane - Got It? - Page 53: 4

36.4

Let $D(20,20)$ be $(x_1,y_1)$. Let $E(30,-15)$ be $(x_2,y_2)$. Use the distance formula: $d=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}$ $d=\sqrt{(30-20)^2+(-15-20)^2}$ $d=\sqrt{10^2+(-35)^2}$ $d=\sqrt{100+1225}$ $d=\sqrt{1325}$ $d=36.4$