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#1 2013-10-24 04:31:59

lisathedork
Member
Registered: 2013-10-24
Posts: 4

Graphing Systems of Linear Equations

How do I graph these?


1. y = (2/3)x - 1
y = -x + 4



2. x + y = 0
3x + y = -4

3. 4x + 3y = -15
y = x + 2



4. x + 2y = -4
4y = 3x + 12



5. y = 2x
x + y = 3



6. x = 3 - 3y
x + 3y = -6


7. y = -2x + 1
y = x - 5

8. y = (1/2)x - 3
y = (3/2)x - 1

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#2 2013-10-24 06:04:05

bobbym
Administrator
From: Bumpkinland
Registered: 2009-04-12
Posts: 84,748

Re: Graphing Systems of Linear Equations

Hi lisa;

Welcome to the forum.

You make a table of x, y values and plot the points on graph paper. Start with the first one:

1. y = (2/3)x - 1

Now just plot point (0,-1) and (1,-1/3) in blue.

y = -x + 4

Click on the drawing below. Now you try the second one.


Now just plot point (0,4) and (1,3) in red.

View Image: 2013-10-24_110211.gif

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

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#3 2013-10-24 07:57:54

lisathedork
Member
Registered: 2013-10-24
Posts: 4

Re: Graphing Systems of Linear Equations

Shouldn't it be like that?

2x - 3y = -2
2(0) - 3y = -2
-3y = -2
y = 2/3
(0, 2/3)
2x - 3(0) = -2
2x = -2
x = -1
(-1, 0)


4x + y = 8
4(0) + y = 8
y = 8
(0, 8)
4x + y = 8
4x + 0 = 8
4x = 8
x = 2
(2, 0)

these are just examples.




Cause I know I have to found the y = mx + b

Last edited by lisathedork (2013-10-24 08:00:25)

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#4 2013-10-24 08:28:55

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,316

Re: Graphing Systems of Linear Equations

hi lisathedork

Welcome to the forum.

You certainly can put x=0 and get y;  and then y=0 and get x.

Any pair of points will be enough to draw the line.

Q5 y = 2x. 

Here using zero will only get one point (0,0) so you'll have to choose another value as well.

eg x = 5 .... y = 2 times 5 = 10 .......(5,10)

You don't need to get them in the format y = mx + b for this

eg

Q5 again

x + y = 3  any two numbers that add to 3 will do so (0,3) (1,2) (2,1) (3,0) (4,-1) 5,-2) .............

Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#5 2013-10-24 09:12:30

lisathedork
Member
Registered: 2013-10-24
Posts: 4

Re: Graphing Systems of Linear Equations

I totally understand now. Thanx.

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#6 2013-10-25 08:59:07

ShivamS
Member
Registered: 2011-02-07
Posts: 3,519

Re: Graphing Systems of Linear Equations

bobbym wrote:

Hi lisa;

Welcome to the forum.
...

First time bobbym calls someone by a shortened name!  smile
Welcome Lisa.

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