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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.



up


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
smile

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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
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 90,864

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.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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