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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: 86,376

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.
Of course that result can be rigorously obtained, but who cares?
Combinatorics is Algebra and Algebra is Combinatorics.

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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: 6,380

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: 3,531

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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