Chapter 10 Counting Methods and Probability - 10.2 Use Combinations and the Binomial Theorem - 10.2 Exercises - Mixed Review - Page 697: 66

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The equation of the perpendicular bisector is: $$(x-a_1)^2+(y-b_1)^2=(x-a_2)^2+(y-b_2)^2$$ We have two points $A(-8,-13)\\B(7,10)$ Substitute the given values: $$(x+8)^2+(y+13)^2=(x-7)^2+(y-10)^2\\x^2+16x+64+y^2+26y+169=x^2-14x+49+y^2-20y+100\\30x+46y-84=0\\15x+23y-42=0$$