graphing equations

Irma Garcia

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Aug 28, 2010
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how do u graph a equation that has decimal? :(
7.1x -3.9y=1.4
how do i graph this?
i dont know how to get started.
 


Determine the two intercepts; plot them, and use a straightedge to draw a line through them.

The x-intercept is on the x-axis, so the y-coordinate must be zero because we don't go up or down.

(x, 0)

Substitute 0 into the equation for y, and solve for x.

The y-intercept is on the y-axis, so the x-coordinate must be zero because we don't go left or right.

(0, y)

Substitute 0 into the equation for x, and solve for y.

 
after i am done with this process do can i get the slope and the x- intercept?
after i substitude the 0 for y i got this...
7.1x-3.9y=1.4
7.1x-3.9(0)=1.4
7.1x=1.4
7.1x/7.1=1.4/7.1
x=197.18 is this correct?
 


Did they ask you to do anything other than graph the equation ? I mean, are you free to graph it using any method?

 


Here is a set of axes for you to use, when you get the coordinates of two points to plot.

The axes go from x = -1 to 1 horizontally and y = -2 to 1.5 vertically.

[attachment=0:35wun6d9]xy-plane.JPG[/attachment:35wun6d9]

 

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Since both intercepts are close to the Origin, let's plot four points, instead of two. It's easy.

In addition to the two intercepts, also find the following.

(-1, y)

(1, y)

In other words, find y when x = -1 and also when x = 1.

Plotting four points will make it easier to draw a fairly accurate line segment.

 


Your work is okay, but you made an arithmetic mistake at the end.

x = 1.4/1.7

x = 0.197

I think we can round that off to 0.2, for graphing purposes.

The x-intercept is (0.2, 0).

What do you get for the y-intercept (0, y) ?

 
well the question is asking me to calculate the slope x intercept and y intercept and then label the intercepts on the graph.
 


This is news to me.

I now suggest that you follow Loren's instruction.

Show us what you get.

 


Multiplying numbers in decimal form by 10 shifts the decimal point one position to the right.

If you multiply both sides by 10 as your first step, you can work toward the y = mx+b form using Whole numbers instead of decimals.

If you multiply both sides by 10, and then solve for y, you'll get the Slope-Intercept form, and then you'll be able to read the slope right from your result (if you understand Slope-Intercept form).

I don't really have any way to determine what you already understand (in your posted exercises) because you never tell us what you're thinking or where you're stuck.

Have you read the post here titled, "Read before posting" ?

 
so i did what u told me
so its: 7.1x-3.9y=1.4
multiply both sides by 10 i got 71x-39y=14 is this correct?
 
Irma Garcia said:
7.1x - 3.9y = 1.4


multiply both sides by 10 i got 71x - 39y = 14 is this correct?

Yes.

Do you know how to solve for y ?

In other words, do you know the two algebraic steps to get the equation into a form that looks like:

y = m * x + b

Hint: m will be a fraction. It's the SLOPE.

If you have no clue how to solve for y, then click HERE to go to the Khan Academy 10-minute video site. Scroll way down to the "Algebra" section and watch the first three videos (Linear Equations 1 through Linear Equations 3).

 


By the way, I hope that your on-line "teacher" is not expecting you to enter the slope into the computer as a decimal number.

Otherwise, we're all wasting our time, here.

Who knows what machine-teachers want ? Do you ?

I mean, did your machine-teacher tell you to enter the slope in decimal form ?

(I've tutored on-line-course students face-to-face at Seattle Central Community College. Half our time is ususally spent trying to figure out what the machine-teacher wants, due to a lack of syntax disclosure and horrible graphics. The people who program these courses aren't too bright.

 


Ah, I see on one of your other threads your statement that you have forgotten everything.

So, of course, you don't know the next two steps.

I think that you should watch the referenced videos above, anyway, but here are the two steps:

Subtract 71x from both sides

Divide both sides by -39

Let's see what you get. 8-)

 
Are you allowed to use a graphing calculator?

Regardless, the first this is to get this in slope-intercept form y= mx + b. This means isolate the y variable. Move the x variable and its coefficient to the right hand side of the equation. Another step may be needed at this point. If y is positive and does not have a coeffiecient (a value in front of the variable) then you have the equation in slope-intercept form. Once it is in this form and you can use a graphing calculator go the Y= editor and enter the information on the right hand side of the equation. You can change the viewing window by going to the window editor. I would change the viewing window to x as -2.5 to 2.5 delta (looks like a little triangle or step to .1) I would change the y values to the same -2.5, 2.5 and .10 for step.

You can use the trace, zoom, and find intercept features for the calculator to give those values. Then I would transfer this data to the graph and label accordingly.
 
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