Math Is Fun Forum

lisathedork

Member

Registered: 2013-10-24

Posts: 36

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

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

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.

---

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.

lisathedork

Member

Registered: 2013-10-24

Posts: 36

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)

Bob

Administrator

Registered: 2010-06-20

Posts: 10,623

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

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

lisathedork

Member

Registered: 2013-10-24

Posts: 36

Re: Graphing Systems of Linear Equations

I totally understand now. Thanx.

ShivamS

Member

Registered: 2011-02-07

Posts: 3,648

Re: Graphing Systems of Linear Equations

Hi lisa;

Welcome to the forum.
...

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