Hi,

I have a question, hope you can help.

Triangle DEF has vertices D(-2,4), E(0,-2) and F(6,2). Determine the equation for AB, the right bisector of DF.

I know that the answer supposed to be 4x-y=5.

Thank you very much!

Printable View

- Jan 27th 2007, 01:13 PMUniverseAnalytic Geometry
Hi,

I have a question, hope you can help.

Triangle DEF has vertices D(-2,4), E(0,-2) and F(6,2). Determine the equation for AB, the right bisector of DF.

I know that the answer supposed to be 4x-y=5.

Thank you very much! - Jan 27th 2007, 01:53 PMUniverse
I got it :)

I tried again and found the answer. - Jan 27th 2007, 01:58 PMticbol
Heck, I'm late again. I type the slowest.

But since you didn't show your solution, let me post mine, anyway.

If AB is the perpendicular bisector of DF, then the slope of AB is the negative reciprocal of the slope of DF.

If AB is the right bisector of DF, then AB passes through the midpoint of DF.

Slope of DF, m1 = (2-4)/(6 -(-2)) = -2/8 = -1/4

Hence, the slope of AB, m2 = -(-4/1) = 4 -----------***

Midpoint of DF = ((-2+6)/2,(4+2)/2) = (2,3) -------***

Then, the point-slope form of the equation of line AB is

(y-y1) = m(x-x1)

(y -3) = 4(x -2)

y -3 = 4x -8

y = 4x -8 +3

y = 4x -5 -----------------answer.

Or, to follow the supposed-to-be answer,

5 = 4x -y

4x -y = 5 ---------------answer.