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Posted: 12/11/2013 11:39:49 AM EST
[Last Edit: 12/11/2013 11:44:22 AM EST by QueenDeNile]
I had a horrible time getting a scanned photo of the page.

My son is suppose to Identify the slope and y-intercept of each graph, then write a corresponding linear equation in slope-intercept form. I was able to figure out 1-3 but then got over my head with the rest. If someone can tell me how to do this, how to understand it, I would be very grateful.




Link Posted: 12/11/2013 11:43:37 AM EST


The answer is 87.





Link Posted: 12/11/2013 11:44:59 AM EST
Y = mx + b
Link Posted: 12/11/2013 11:45:19 AM EST
Rise over Run
Link Posted: 12/11/2013 11:45:25 AM EST
Odd-numbered answers are in the back
Link Posted: 12/11/2013 11:45:51 AM EST
I think #4 is y=2
Link Posted: 12/11/2013 11:47:26 AM EST
Do you know about Khan Academy?
Link Posted: 12/11/2013 11:47:28 AM EST
[Last Edit: 12/11/2013 11:48:53 AM EST by WhyTanFox]
Four and six are kinda trick questions, but what was the problem solving 5?

ETA What did you get trying to solve 5?
Link Posted: 12/11/2013 11:48:40 AM EST
Don't they explain it at the begining of the lesson?

Or google how to do it.
Link Posted: 12/11/2013 11:49:50 AM EST
Slope intercept form is y=mx +b. Y is the height on your graph. M is the slope. X is your independent variable. And b is the height of the line where it crosses the y axis.

To find the slope find the ratio of the amount the line rises divided by the amount it "runs" or moves horizontally. In the case of a purely horizontal line the equation is y=height of line
Link Posted: 12/11/2013 11:51:36 AM EST
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Originally Posted By WhyTanFox:
Four and six are kinda trick questions, but what was the problem solving 5?

ETA What did you get trying to solve 5?
View Quote

I got b=0, m = -3+5 but the back of the book states: m= -2/3 b=0 & y = -2/3 so I obviously do not know what I'm doing!
Link Posted: 12/11/2013 11:51:58 AM EST
Link Posted: 12/11/2013 11:52:27 AM EST
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Originally Posted By jh1990:
Slope intercept form is y=mx +b. Y is the height on your graph. M is the slope. X is your independent variable. And b is the height of the line where it crosses the y axis.

To find the slope find the ratio of the amount the line rises divided by the amount it "runs" or moves horizontally. In the case of a purely horizontal line the equation is y=height of line
View Quote
okay now this makes sense. Let me try. Thank you.
Link Posted: 12/11/2013 11:54:17 AM EST
What is his level of participation in solving these problems? Sounds like you are the one doing the homework assignment.
Link Posted: 12/11/2013 11:58:54 AM EST
Proper arfcom math protocol is to only misunderstand/hate DIFFERENT ways of teaching mathematics. There is no call for a thread like this.
Link Posted: 12/11/2013 11:59:05 AM EST
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Originally Posted By thelastgunslinger:
What is his level of participation in solving these problems? Sounds like you are the one doing the homework assignment.
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so far none. He's sick and hasn't been to class so I'm trying to understand them before I teach it to him.
Link Posted: 12/11/2013 11:59:51 AM EST
Do you even lift bro?
Link Posted: 12/11/2013 12:00:11 PM EST
[Last Edit: 12/11/2013 12:08:26 PM EST by absael]
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Originally Posted By QueenDeNile:

I got b=0, m = -3+5 but the back of the book states: m= -2/3 b=0 & y = -2/3 so I obviously do not know what I'm doing!
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Originally Posted By QueenDeNile:
Originally Posted By WhyTanFox:
Four and six are kinda trick questions, but what was the problem solving 5?

ETA What did you get trying to solve 5?

I got b=0, m = -3+5 but the back of the book states: m= -2/3 b=0 & y = -2/3 so I obviously do not know what I'm doing!
-3+5=2. Lines with positive slope rise from left to right, so you can tell at a glance that this line has negative slope. Also, a slope of 1 is 45 deg. (it rises 1 unit for every 1 unit it runs), so you can tell at a glance that the slope is larger than -1 (IOW, it's between 0 and -1).

ETA: I tried to rewrite the last part to make it less confusing, but I'm not sure that I succeeded. What I mean is that a line with a positive slope of greater than one will be steeper than 45 deg. and rise from left to right. A line with a slope of less than -1 (think of numbers on the number line, -2 is less than -1) will fall from left to right, and be steeper than 45 deg.
Link Posted: 12/11/2013 12:01:35 PM EST
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That video is doing a much better job explaining it than I would.
Link Posted: 12/11/2013 12:06:30 PM EST
[Last Edit: 12/11/2013 12:09:56 PM EST by InfiniteGrim]
4)

Y Intercept.... 2

Equation y = 0x + 2
y = 2


5)

Y Intercept........ 0

Equation y = -(2/3)x +0
y = -(2/3)x

6)

Y Intercept.......NONE

Equation x = 2



Whenever these is a horizontal, or a vertical line it means that either X or Y is the same for all values of Y or X.

So for number 6, X will always be 2 no matter what value of Y. How can this be? Y in the equation is multiplies by 0 so whatever number you put in the equation, the Y value will never effect the outcome.
Link Posted: 12/11/2013 12:09:42 PM EST
Whythefox you did well. Thank you.
Link Posted: 12/11/2013 12:12:11 PM EST
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Originally Posted By 57fairlane:
Odd-numbered answers are in the back
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Genius
Link Posted: 12/11/2013 12:14:45 PM EST
[Last Edit: 12/11/2013 12:16:27 PM EST by Fieldgeek]
m is the slope.
b is the y intercept.
Slope intercept form is y=mx+b.


Problem 4
Lets find the Y intercept (outside of just looking at it).

We need to find the equation as it passes through the points, 2,2 (x1,y1) and -2,2 (x2,y2)

We know Y = 2 at a value of X = 0.

Slope formula is

m = (y1) - (y2) / (x1) - (x2)
m = (2 - 2) / (2 - -2)
m = 0 / 4
m = 0

Now we know the slope is 0.
Find y intercept (b) where the slope is 0 (m, which we figured out above) and for point -2,2 (any point on line)
y=mx+b
2 = 0*-2 + b
2 = b
b = 2

Now solve the equation.
y = mx+b
y = 0x + 2
The equation in this case will simply be y = 2.

Thus:
Your y intercept is 2
Your slope is 0
Your equation is y = 2
Link Posted: 12/11/2013 12:16:02 PM EST
288
Link Posted: 12/11/2013 12:27:43 PM EST
Would you like me to walk through the rest of the problems in the same way I did above or have you received enough information?
Link Posted: 12/11/2013 12:38:44 PM EST
[Last Edit: 12/11/2013 12:39:40 PM EST by Couch-Commando]
Take two points to find the slope.

Suppose the points are (x1,y1) and (x2,y2).

Then, the slope is m=(y2-y1)/(x2-x1).

The point intercept form of a linear curve is y=mx+b.

You know m.

Now pick a point, such as (x1,y1) and plug it in.

y1=mx1+b.

Solve for b.

b=y1-mx1.

Now you have m and b. Write out the linear curve.

y=mx+b.

Check your work by plugging in x2 and making sure that you get y2.

ETA: Let me know if this is not clear. If not, then I will type it up in LaTex so it looks nice and send it to you via IM.
Link Posted: 12/11/2013 12:50:11 PM EST
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Originally Posted By Fieldgeek:
Would you like me to walk through the rest of the problems in the same way I did above or have you received enough information?
View Quote

I've got it, thank you! I didn't understand the slope but I've got it. I haven't done this in 30 years though so more than likely I'll struggle tomorrow.
Link Posted: 12/11/2013 6:01:33 PM EST
To find the best fit line you need to use the "least squares method" and calculate the R^2 value.

Excel can do this for you.
Link Posted: 12/11/2013 6:04:22 PM EST
This doesn't help, but I thought it was cool
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