anonymous
  • anonymous
Hi can someone help me with this table and graph stuff for algebra?
Mathematics
  • Stacey Warren - Expert brainly.com
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katieb
  • katieb
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anonymous
  • anonymous
I guess it could be either linear or cubic. It kind of looks like there's an inflection point between 1974 and 1975. Do you have to find the equation by hand?
anonymous
  • anonymous
it doesn't really say, but it would probably be for the best.
anonymous
  • anonymous
ok well if you have to do it by hand, it's probably linear. least square regression?

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anonymous
  • anonymous
It doesn't say specifically but that should work.
anonymous
  • anonymous
you have to change your table to do this. The y-column is fine the way it is. The x-column needs to start at 0. So let 1885 be year 0 and let x be years after 1885. So like 1917 will be 32, 1919 will be 34, etc
anonymous
  • anonymous
okay wait I think I misinterpreted what you typed. I have to change the table to find an equation?
anonymous
  • anonymous
Yeah, we're looking for an equation in y = mx + b form. If you leave the table like that it will skew the y-intercept ( I believe)
anonymous
  • anonymous
right okay I think I follow you a little.
anonymous
  • anonymous
this is making the gears in my head spin lol I know the equation has to be y=mx + b
anonymous
  • anonymous
This is one I helped someone with last night. Scroll to about the middle of the page. Do the formulas for a and b look familiar? http://openstudy.com/users/peachpi#/updates/55d7dbd9e4b02663346b9fa8
anonymous
  • anonymous
oh yeah! I've seen those before. I mean I always get the numbers mixed up. I wouldn't know where to put what.
anonymous
  • anonymous
that's fine. Just start with adjusting the years and we'll go from there
anonymous
  • anonymous
I feel like that table on that page or whatever has specific numbers for the x's and y's. I wouldn't know which ones to apply for my situation.
anonymous
  • anonymous
Your y's are going to be the stamp's costs (0.02, 0.03, 0.02, 0.03, etc.) Your x's are going to be years since 1885 (0, 32, 34, 47, etc). Subtract 1885 from each year to get these
anonymous
  • anonymous
oh that's how you got those, ok.
anonymous
  • anonymous
If you have excel, google docs, or some other spreadsheet program it will do the calculations for you and you just have to arrange the table
anonymous
  • anonymous
I had excel but the trial ended. I don't really have any way to do this. I don't know I gotta think about this.
anonymous
  • anonymous
for that girl you did a table that was x|y|x^2|xy is that what I have to do?
anonymous
  • anonymous
yeah
anonymous
  • anonymous
oh man okay x would start with 0? I think you said. I'm sorry I'm so hopeless I'm getting myself confused all over again.
anonymous
  • anonymous
or would the x and y columns look exactly like my table? and then I would multiply x by itself and then I multiply x and y?
anonymous
  • anonymous
hold up. I don't think those are going to be the right equations anyway. I think this might be exponential. It just doesn't look so on your graph because the years aren't evenly spaced. This is what I get with an evenly spaces x-axis
anonymous
  • anonymous
|dw:1440245393715:dw|
anonymous
  • anonymous
so I did my graph wrong? Or that's a new graph over my original graph?
anonymous
  • anonymous
no, your graph is wrong. You used 1 square for each difference in years, but the differences aren't all the same
anonymous
  • anonymous
so do I need to redo the years on my graph? I actually wasnt sure how to space them. I only had like 25 spaces. Yeah the years aren't spaced correctly.
anonymous
  • anonymous
what spacing would you recommend I use?
anonymous
  • anonymous
I can use the spacing you used for the y axis, but I'm not sure for the x axis.
anonymous
  • anonymous
Ok so we're going from 1885 to 2012, that's 127 years. Divide by 25 to get 5.02, so make every space 6 years to have a little extra room on the right
anonymous
  • anonymous
Don't put the actual years on the graph. so start at 0, then 6, 12, 18 etc. Then use a label that says "Years since 1885"
anonymous
  • anonymous
I'm sorry for being so confused. I'm really trying to understand this
anonymous
  • anonymous
so i didn't label the years but started with 0 and ended with 138 (that's as far as my graph will let me go)
anonymous
  • anonymous
0 represents 1885. 6 represents 1891. 12 represents 1897. Even though 1891 won't be a point on the graph, we have to show it on the x-axis to show how long it's taking the price to rise at the beginning. 1917 is 32 years after 1885. So that point will be about 5 or 6 grid lines right of the first point
anonymous
  • anonymous
okay I'm gonna need a much bigger graph
anonymous
  • anonymous
No your graph is fine. 2012 is 127 years after 1885. Your graph is showing 138 years after, so we have a little extra. That's exactly what we want
anonymous
  • anonymous
okay
anonymous
  • anonymous
Have you done the thing where you subtract 1885 from all the years yet?
anonymous
  • anonymous
is the y axis okay? I went by 2's on there?
anonymous
  • anonymous
yes the y-axis is good
anonymous
  • anonymous
I wasn't sure what you meant by that.
anonymous
  • anonymous
like this 1885 - 1885 = 0 1917-1885 = 32 1919 - 1885 = 34
anonymous
  • anonymous
oh okay well I'll do all those and get back to you okay?
anonymous
  • anonymous
ok.
anonymous
  • anonymous
almost done...
anonymous
  • anonymous
ok
anonymous
  • anonymous
ok. At the bottom of the page are the equations for curve fitting an exponential function (lowercase a and b). http://mathworld.wolfram.com/LeastSquaresFittingExponential.html
anonymous
  • anonymous
then I need to square the x's and then multiply x and y
anonymous
  • anonymous
oh man yikes okay
anonymous
  • anonymous
this one isn't linear so the equations are different. Have you seen those before? I had a hard time even finding them, so I'm wondering if you're supposed to do this using technology as opposed to hand
anonymous
  • anonymous
No I haven't really seen them before (hence my yikes lol) This is on a worksheet so I just assumed it was by hand
anonymous
  • anonymous
I feel like my heads gonna explode.
anonymous
  • anonymous
If you have or want to create a google account, google docs will calculate the curve once you enter the data in their spreadsheet
anonymous
  • anonymous
I just have a really hard time thinking they want an algebra student to do this by hand :/
anonymous
  • anonymous
I've never used spreadsheets before. How do I see the curve in the spreadsheet?
anonymous
  • anonymous
you have to enter the table and then create the chart. I can walk you through it. Search for google docs then sign in to create a spreadsheet
anonymous
  • anonymous
okay I'm on the spreadsheet (that link you gave me that you did last night since her graph thing was linear and my is expo than how I find an equation is different?
anonymous
  • anonymous
Linear is y = mx + b Exponential is \(y=ab^x\)
anonymous
  • anonymous
okay gotcha well i'm on the spread sheet now
anonymous
  • anonymous
can you explain to me why it is expo? I don't think we went over that
anonymous
  • anonymous
ok. so now make columns for x and y. Put the x column to the left and enter the numbers you got by subtracting (0, 32, etc) and another for the prices
anonymous
  • anonymous
make the correct graph first. It will be easier to understand that way. You really wouldn't know whether it was linear or exponential once you see the graph.
anonymous
  • anonymous
*until you see the graph
anonymous
  • anonymous
so in the A column put 0 32 34 47 all the way ↓ to 127 In the B column 0.02 0.03 0.02 0.03 ↓ 0.45
anonymous
  • anonymous
okay let me do all of that
anonymous
  • anonymous
I labeled the two sides of the table (years were x) (y were costs)
anonymous
  • anonymous
okay now what do I do?
anonymous
  • anonymous
ok. now highlight the cells with numbers in them and go to the INSERT menu at the top and select CHART
anonymous
  • anonymous
stupid question - how do I highlight them w/o highlight the little grey column on the left?
anonymous
  • anonymous
That's going to highlight automatically so you know which cells are selected. It's fine. Once you pick Chart A box should pop up with named Chart Editor with Recommendations, Chart Types, and Customization tabs
anonymous
  • anonymous
I don't think it matters
anonymous
  • anonymous
ok
anonymous
  • anonymous
okay I did insert and selected chart
anonymous
  • anonymous
i'm in the chart editor
anonymous
  • anonymous
One of the recommended charts should a grid showing dot. Select that one and hit INSERT at the bottom
anonymous
  • anonymous
okay
anonymous
  • anonymous
done
anonymous
  • anonymous
do you want me to screencap and upload it to make sure it looks good?
anonymous
  • anonymous
yes please
anonymous
  • anonymous
not sure if that looks right
anonymous
  • anonymous
This is mine
1 Attachment
anonymous
  • anonymous
hm seems like I missed something
anonymous
  • anonymous
For the most part it looks right. Maybe one of us made a typo when entering the points
anonymous
  • anonymous
yeah could be. I really don't think they will notice too much. it's fine
anonymous
  • anonymous
I'll leave it to you to check, but we can go on so you know how to get the equation
anonymous
  • anonymous
okay
anonymous
  • anonymous
Do you notice how it almost flat toward the left and then increases steeply toward the right? That's how I know it's exponential
anonymous
  • anonymous
right
anonymous
  • anonymous
|dw:1440249587962:dw|
anonymous
  • anonymous
The graph on the right is linear functions. They have the same slope everywher
anonymous
  • anonymous
I see
anonymous
  • anonymous
To get the equation of your graph hit the little triangle on the top right corner of the graph and select ADVANCED EDIT
anonymous
  • anonymous
okay
anonymous
  • anonymous
Then go down to where it has TRENDLINE and select EXPONENTIAL For LABEL select USE EQUATION
anonymous
  • anonymous
okay
anonymous
  • anonymous
then input?
anonymous
  • anonymous
or update I guess
anonymous
  • anonymous
oh yeah hit update
anonymous
  • anonymous
ok
anonymous
  • anonymous
do you see the equation to the right of the graph?
anonymous
  • anonymous
how do I see all of it?
anonymous
  • anonymous
you can make the chart bigger. grab one of the handles on the corner to stretch it
anonymous
  • anonymous
so that's my equation then
anonymous
  • anonymous
yeah mine is 8.66 instead of 9.538 yeah that's the equation.
anonymous
  • anonymous
can you tell me your full equation just incase mine was the one that wasn't 100% correct?
anonymous
  • anonymous
Mine was (8.661E-3)e^(0.03x)
anonymous
  • anonymous
awesome thank you
anonymous
  • anonymous
You should probably write it in decimal form though. So yours would be 0.009538e^(-0.03x)
anonymous
  • anonymous
(move the decimal point left 3 times and drop the E)
anonymous
  • anonymous
math teachers don't generally like E format
anonymous
  • anonymous
don't put it in y=ab^x form?
anonymous
  • anonymous
It is. a = 0.009538 b = e^0.03
anonymous
  • anonymous
oh okay I see didn't know if y= is relevant or not.
anonymous
  • anonymous
It should be y = 0.009538e^(0.03x) as your final equation. (the - I put there was a mistake)
anonymous
  • anonymous
okay
anonymous
  • anonymous
so how can I use that equation to predict from 2013-2022 Do I change something in it?
anonymous
  • anonymous
or bring the costs back in?
anonymous
  • anonymous
For 2013 - 2022, you have to plug the x-values into the equation to get predictions. For example: 2013 - 1885 = 128 So plug in 128 into your equation y = 0.009538e^(0.03*128) y = 0.44376 y = $0.44
anonymous
  • anonymous
$0.46
anonymous
  • anonymous
yeah $0.46
anonymous
  • anonymous
awesome! Okay I just want to thank you so much for everything. Like you are a life saver. <333 The best
anonymous
  • anonymous
You're welcome :)

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