Describe and write an equation for the locus of points equidistant form A(a_x, a_y) and B(b_x,b_y)? Test what you derived for P_A(-2,5) and P_B(6,1)?

1 Answer
Nov 3, 2016

-2x+y+1=0

Explanation:

Calling p=(x,y) we are looking for p such that

norm(p-A)=norm(p-B) or equivalently

norm(p-A)^2=norm(p-B)^2 so

(x-a_x)^2+(y-a_y)^2=(x-b_x)^2+(y-b_y)^2

simplifying we get at

2(a_x-b_x)x+2(a_y-b_y)y-a_x^2-a_y^2+b_x^2+b_y^2=0

which is the equation of a line equidistant from A and B

If A=(-2,5) and B=(6,1) then

2(-2-6)x+2(5-1)y-4-25+36+1=0 or

-2x+y+1=0