Chapter 9 Quadratic Relations and Conic Sections - 9.1 Apply the Distance and Midpoint Formulas - 9.1 Exercises - Skill Practice - Page 618: 40

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Find the midpoint of the line segment $(\frac{x_1+x_2}{2},\frac{y_1+y_2}{2})=(\frac{3+7}{2},\frac{1+5}{2})=(5,3)$ Calculate the slope of AB: $m=\frac{y_2-y_1}{x_2-x_1}=\frac{6-3}{2-5}=-1$ Use point-slope form: $y-3=-1(x-5)\\y=-x+8$