# Need some help with graphing a system of equations

• Mar 29th 2008, 02:06 PM
aim
Need some help with graphing a system of equations
I need to graph a system of equations. I'll write it down below. Sorry in advance if it's hard to understand.

4x - 3y = 5 (first half of the system)
-3y = -4x + 5
-3y/-3 = -4x/-3 + 5/-3
y = 4/3x - 5/3
m=4/3 b=- 5/3

y = 4/3x - 7/3 (second half of the system)
m=4/3 b=- 7/3

Have I done everything right so far? What do I do next?
• Mar 29th 2008, 03:10 PM
mr fantastic
Quote:

Originally Posted by aim
I need to graph a system of equations. I'll write it down below. Sorry in advance if it's hard to understand.

4x - 3y = 5 (first half of the system)
-3y = -4x + 5
-3y/-3 = -4x/-3 + 5/-3
y = 4/3x - 5/3
m=4/3 b=- 5/3

y = 4/3x - 7/3 (second half of the system)
m=4/3 b=- 7/3

Have I done everything right so far? What do I do next?

Yes. But are you able to use what you've done to draw the graphs of these two lines?

Personally, I draw a line by finding two points on it - usually the x-intercept and the y-intercept.
• Mar 29th 2008, 03:35 PM
aim
Quote:

Originally Posted by mr fantastic
Yes. But are you able to use what you've done to draw the graphs of these two lines?

Personally, I draw a line by finding two points on it - usually the x-intercept and the y-intercept.

I've never had to graph a system of equations involving fractions so I'm not really sure.
• Mar 29th 2008, 03:39 PM
mr fantastic
Quote:

Originally Posted by aim
I've never had to graph a system of equations involving fractions so I'm not really sure.

So ....?

4x - 3y = 5:

x-intercept: Substitute y = 0 and solve for x. x = 5/4. Mark it on the x-axis.
y-intercept: Substitute x = 0 and solve for y. y = -5/3. Mark it on the y-axis.

Draw a line passing through the x-intercept and the y-intercept. Done.

Why should fractions cause problems?
• Mar 29th 2008, 03:54 PM
aim
Quote:

Originally Posted by mr fantastic
So ....?

4x - 3y = 5:

x-intercept: Substitute y = 0 and solve for x. x = 5/4. Mark it on the x-axis.
y-intercept: Substitute x = 0 and solve for y. y = -5/3. Mark it on the y-axis.

Draw a line passing through the x-intercept and the y-intercept. Done.

Why should fractions cause problems?

I've never had to graph a y-intercept that was a fraction before. Should I use the numerator as the rise and denominator as the run? Or?
• Mar 29th 2008, 03:59 PM
mr fantastic
Quote:

Originally Posted by aim
I've never had to graph a y-intercept that was a fraction before. Should I use the numerator as the rise and denominator as the run? Or?

The y-intercept is where the line cuts the y-axis. It's a number. You mark it in on the y-axis.

The x-intercept is where the line cuts the x-axis. It's a number. You mark it in on the x-axis.

Have you been taught what a y-intercept is and what an x-intercept is?
• Mar 29th 2008, 04:05 PM
aim
Quote:

Originally Posted by mr fantastic
The y-intercept is where the line cuts the y-axis. It's a number. You mark it in on the y-axis.

The x-intercept is where the line cuts the x-axis. It's a number. You mark it in on the x-axis.

Have you been taught what a y-intercept is and what an x-intercept is?

4x - 3y = 5 (first half of the system)
-3y = -4x + 5
-3y/-3 = -4x/-3 + 5/-3
y = 4/3x - 5/3
m=4/3 b=- 5/3

b is the y-intercept, right? Well, for the questions I've had so far b has always equaled a whole number. If it was b=7 I would put a point on (0,7). The problem is that I don't know how to graph the y-intercept when it's a fraction. Does that make sense?
• Mar 30th 2008, 04:09 PM
aim
I still need help for this, if anyone is willing. Sorry to be naggy, but I really need help understanding how to use these fractions when graphing.

PS: I'm totally clueless, so if you decide to help me please be patient. (Doh)