Originally Posted by

**mrszone** This is a fuller description of what I have so far:

Find the equation of the perpendicular bisector of AB when

A=(3,1) B=(-1,-11)

This is what I have worked out so far:

-1 - 3 = -4 which is the run

-11 - 1 = -12 which is the rise

-12 / -4 = 3 which is the slope

the negative reciprocal is -1/3

the midpoint is (1/2(3+-1)), (1/2(1+-11))

which gives you a midpoint of 1,-5

this leaves an equation of y - -5 = -1/3(x-1)

y + 5 = -1/3(x-1)

all the exercise examples show the final equation after multiplying out the brackets and this is what I am trying to do.