## stright line equation problem :S stuck on a question

### keiran

Posted 14 June 2005 - 06:24 PM

Hey im doing some homework for maths but am stuck hope someone can help. Here is the question:

Find the equation of the perpendicular bisector of the line joining each pair of points.

C(-2,0) and E(8,1)

So heres what im getting:

Midpoint = ((X1 + X2) / 2) , ((Y1 + Y2) / 2)
= ((-2 + 8) / 2) , ((0 + 1) / 2)
= (3,1/2) < 1/2 equals a half just in case its not clear

M = Y2 - Y1 / X2 - X1
= 1 - 0 / 8 - (-2)
= 1/10 < 1/10 also a fraction

meaning

M = -10/1
A = 3
B = 1/2

so the form of the equation should be
Y - B = M (X - A)
Y - 1/2 = -10/1 (X - 3)

But my problem is I don't know what to do when I have a point which is a half :S Does anyone know ?

20X + 2Y - 61 = 0 < This answer is from the book and has been re arranged to the form - AX + BY + C = 0

Keiran

### dfx

Posted 14 June 2005 - 07:11 PM

Y - 1/2 = -10 ( x - 3)

Expand the brackets:

Y - 1/2 = -10x + 30

You need to get rid of the 2 at the bottom, so you multiply by 2 THROUGH OUT (on both sides of the equation, by each term):

So you have:
2 * (y - 1/2) = 2 * (-10x + 30)

( "*" is for multiplication, to avoid confusion with "x" which is X)

So you get:

2y - 2/2 = -20x + 60

2/2 is just 1

so

2y - 1 = -20x + 60

Bring it all over to one side:

2y + 20x -1 - 60 = 0

So:

20x + 2y - 61 = 0.

I take it you're in Standard Grade/starting Highers... which is why I've gone a lil slowly. Hope that helps. Good luck

### keiran

Posted 14 June 2005 - 07:14 PM

thanks a lot, I now understand what to do Yes your right just starting higher maths

Keiran

### JiLL

Posted 14 June 2005 - 07:30 PM

good luck with higher maths!!!

I did it last year nd found it rly tuff but if u get ur head down nd study really hard for it, u'll be fine!!

### dfx

Posted 14 June 2005 - 07:53 PM

Yep, its one of those things that you need to work hard at and most importantly practice lots and lots.

### Allana

Posted 18 June 2005 - 07:00 PM

Hey i'm just new to this message board. I recently sat my Maths standard grade and didn't think it went as well as i would have liked - i'm hoping to get a 2. Do you think it is still possible for me to get at least a B in higher maths, even though i found the s.grade exam hard?

### dfx

Posted 19 June 2005 - 01:23 PM

Higher Math isn't really hard, its just quite a large jump if you ask me from what I've seen with my fellow classmates. You need to be very comfortable with using indices, fractions, basic algebra, factorisation of quadratics, basic basic stuff like that. Once you're comfortable with it, the theory is really a breeze. That said, you still need to put in a decent amount of effort depending obviously on how comfortable you are - anything from upto an hour or so a night.

I'd say if you got a head start over the summer holidays, got to grips with your basics and get comfortable with your math, and possibly even start doing bits of the Higher course, you stand a really good chance of a good grade.

Oh btw, welcome and have fun round here

### Allana

Posted 19 June 2005 - 02:51 PM

Thanks for the advice. I'm not one for slacking off and leaving revision to the last minute, so hopefully if i stick at it i will be ok.
Thanks for the welcome

### The Wedge Effect

Posted 20 June 2005 - 10:01 AM

QUOTE(Allana @ Jun 18 2005, 08:00 PM)
Hey i'm just new to this message board. I recently sat my Maths standard grade and didn't think it went as well as i would have liked - i'm hoping to get a 2. Do you think it is still possible for me to get at least a B in higher maths, even though i found the s.grade exam hard?

I found my Standard Grades hard when I sat it, but Higher Maths seem to be more easier to understand once you've got a good grasp of it. I thought I would fail but got a 1 in my SGs. That just goes to show you anyone can do it. You can do it! Be positive!

### Allana

Posted 20 June 2005 - 04:00 PM

QUOTE(Wedge37 @ Jun 20 2005, 10:01 AM)
QUOTE(Allana @ Jun 18 2005, 08:00 PM)
Hey i'm just new to this message board. I recently sat my Maths standard grade and didn't think it went as well as i would have liked - i'm hoping to get a 2. Do you think it is still possible for me to get at least a B in higher maths, even though i found the s.grade exam hard?

I found my Standard Grades hard when I sat it, but Higher Maths seem to be more easier to understand once you've got a good grasp of it. I thought I would fail but got a 1 in my SGs. That just goes to show you anyone can do it. You can do it! Be positive!

thanks for the advice, although im pretty sure i've not got a 1. Damn it! I had worked so hard aswell and got good grades all year. Hopefully next year will bring more luck