# I have a question about a problem in the first chapter of precalc?

• Sep 5th 2012, 04:17 PM
Tedward570
I have a question about a problem in the first chapter of precalc?
Here is the question which I am trying to solve:
Triangle ABC has vertices at A (-1,4) B (8,2) C (11,-4)
1.Find the slope of side AC (I think it is -2/3)
2.Find the slope of the altitude from B to side AC
3.Find the equation in slope intercept form of the altitude from B to side AC

Any help would be appreciated. Thank You!
• Sep 5th 2012, 04:39 PM
skeeter
Re: I have a question about a problem in the first chapter of precalc?
1. correct

2. hint: the altitude from B to AC is perpendicular to AC ... what do you remember about slopes of lines that are perpendicular?

3. hint: point-slope form of a linear equation
• Sep 5th 2012, 06:35 PM
Tedward570
Re: I have a question about a problem in the first chapter of precalc?
Ok so is #2 then 3/2 since it is the opposite reciprocal? Is #3 then y=3/2x-10/3? If someone could now at this point just give me the answer and how they got it would be appreciated.
• Sep 6th 2012, 03:11 AM
skeeter
Re: I have a question about a problem in the first chapter of precalc?
10/3 for a y-intercept ?

the altitude has a slope of 3/2, and it passes thru point B (8,2).

point-slope form ...

$\displaystyle y - 2 = \frac{3}{2}(x - 8)$