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## #1 2006-08-31 22:32:35

Devantè
Real Member
Registered: 2006-07-14
Posts: 6,400

### Writing Linear Equations Given Two Points

Exercises on Writing Linear Equations Given Two Points

Write an equation of the line that passes through the given two points.

1. (1,2) , (21,-58)
2. (5,1) , (11,-23)
3. (1,5) , (7,8)
4. (3,8) , (37,-60)
5. (29,48) , (55,9)
6. (8,-7) , (133,668)
7. (-6,-6) , (78,183)
8. (-19,10) , (47,-210)
9. (0,5) , (45,    -220)
10. (22,-41) , (58,-23)
11. (-39,-27) , (41,357)
12. (-2,-8) , (42,-63)
13. (-10,-26) , (40,-36)
14. (-5,-24) , (19,-136)
15. (-5,4) , (35,64)
16. (3,-1) , (31,-85)
17. (37,49) , (47,24)
18. (-11,-6) , (27,-215)

--------------------------------

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## #2 2006-09-16 13:20:24

Prakash Panneer
Member
Registered: 2006-06-01
Posts: 110

### Re: Writing Linear Equations Given Two Points

This is the formula for finding the equation of line when the two points ( x1, y1) and (x2, y2) are given,

(y - y1)(x2 - x1) = (x - x1) (y2 - y1).

Using this formula, we can find an equation of a line for the given points.

Letter, number, arts and science
of living kinds, both are the eyes.

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## #3 2007-01-24 23:55:54

littlelittle
Member
Registered: 2007-01-24
Posts: 10

### Re: Writing Linear Equations Given Two Points

Hi

Stuck again..

An equation is y = mx + b where m is the slope ie. y1-y2/x1-x2.

How do i calculate 'b' without drawing n connecting the points?

Prakash - how do i put your formula to work?  Can you do 1 prob for me please?

Thanks
S

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## #4 2007-01-25 00:04:59

Toast
Real Member
Registered: 2006-10-08
Posts: 1,321

### Re: Writing Linear Equations Given Two Points

Well, let's take for example, the coordinates (1,4) (-3, 5).
The coordinates are of the form (x1, y1) (x2, y2), so we can substitute them into the formula:
(y - y1)(x2 - x1) = (x - x1) (y2 - y1)
(y - 4)(-3 - 1) = (x - 1)(5 - 4)
(y - 4)(-4) = (x - 1)(1)
Using the distributive law:
-4(y - 4) = 1(x-1)
-4y + 16 = x - 1
-4y = x - 17
∴                   y = -1/4x + 17/4

(I personally don't use this method [although it would probably benefit me if I did], instead, I find the gradient (y2-y1)/(x2-x1), then substitute the coordinate points in to solve for c)

Last edited by Toast (2007-01-25 00:08:21)

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## #5 2007-01-25 02:39:42

littlelittle
Member
Registered: 2007-01-24
Posts: 10

### Re: Writing Linear Equations Given Two Points

Thanks Toast.

Its now clear to me.

Thanks again

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## #6 2010-09-29 23:30:57

smithlanger
Member
Registered: 2010-09-29
Posts: 1

### Re: Writing Linear Equations Given Two Points

sounds good to me

smith

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## #7 2010-09-30 07:32:16

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: Writing Linear Equations Given Two Points

Hi smith;

Welcome to the forum. There are actually easier ways to do that.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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