Chapter 9 Quadratic Relations and Conic Sections - 9.1 Apply the Distance and Midpoint Formulas - Guided Practice for Examples 1 and 2 - Page 615: 2

scalene

The distance formula from $P_1(x_1,y_1)$ to $P_2(x_2,y_2)$ is $d=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}$. Hence here: $RS=\sqrt{(-1-5)^2+(3-2)^2}=\sqrt{37}$, $RT=\sqrt{(-1-3)^2+(3-6)^2}=\sqrt{25}=5$, $ST=\sqrt{(3-5)^2+(6-2)^2}=\sqrt{24}$, thus the triangle is scalene