Posted: 10/6/2009 9:14:30 PM EDT
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I am studying functions, graphs and such in my math class right now. I just finished the online quiz in preparation for the online test, which I have to pass before taking the written test.
The online quiz had 19 questions and out of those I had two points marked incorrectly. One of them I have a huge dispute with. It's not that the score counts, because the only thing in this class that counts are the written tests. That said, I want some input so that I can understand this. The problem that I am flustered over was this: Graph a line for the equation 2x+4y=8 There were no additional instructions. My solution to the equation was y=-1/2x +2 So from this I know that m=-1/2 and the y intercept is (0,2) The program has a graphing tool with which you can graph a line in answer to the problem. From the graphing tool I made the points for my line (0,2) and (2,1). This of course is -1 on the y axis and +2 on the x axis. The computer marked it wrong said that the correct line was (0,2) (4,0). It is the exact same fucking line running through the exact same fucking points, only that they moved down two increments of the slope instead of one increment. Any ideas as to why they're right and I'm wrong? |
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Quoted:
I am studying functions, graphs and such in my math class right now. I just finished the online quiz in preparation for the online test, which I have to pass before taking the written test. The online quiz had 19 questions and out of those I had two points marked incorrectly. One of them I have a huge dispute with. It's not that the score counts, because the only thing in this class that counts are the written tests. That said, I want some input so that I can understand this. The problem that I am flustered over was this: Graph a line for the equation 2x+4y=8 There were no additional instructions. My solution to the equation was y=-1/2x +2 So from this I know that m=-1/2 and the y intercept is (0,2) The program has a graphing tool with which you can graph a line in answer to the problem. From the graphing tool I made the points for my line (0,2) and (2,1). This of course is -1 on the y axis and +2 on the x axis. The computer marked it wrong said that the correct line was (0,2) (0,4). It is the exact same fucking line running through the exact same fucking points, only that they moved down two increments of the slope instead of one increment. Any ideas as to why they're right and I'm wrong? I think the quiz answers are wrong. The intercepts are (0,2) and (4,0) so maybe someone entered the answers in the system wrong? The point (0,4) doesn't seem to work, as 2(0)+4(4) =! 8. And a straight line with points at (0,2) and (0,4) is the y axis. |
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I think the computer is wrong about 0,4. ETA: The correct x-intercept is 4,0 so either way you are wrong. Here's an online calculator that will do it http://www.coolmath.com/graphit/ |
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Quoted:
The program has a graphing tool with which you can graph a line in answer to the problem. From the graphing tool I made the points for my line (0,2) and (2,1). This of course is -1 on the y axis and +2 on the x axis. The computer marked it wrong said that the correct line was (0,2) (0,4). Is that correctly typed? Because that would be a straight vertical line, not corresponding to the equation, not a function, and complete bullshit. Either you typed it wrong in your post or whoever made the quiz typed it wrong in the computer. (4,0) is correct. eta: (2,1) is also a point on the line, so if they just wanted a point on the line then it should work just fine. |
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I know what they did!
Cocksuckers! The method that we have been taught is to do all calculations based on the y=mx+b formula to find the slope AND y intercept. So to get the problem in y=mx+b form: 2x+4y=8 = 2x-2x+4y=-2x+8 = 4y/4=-2/4x-8/4 = y=-2/4x+2 So, the y intercept is 2 and the coordinates are (0,2) The slope is -2/4. slope =rise/run So, if you start at (0,2) and your rise is -2 and your run is +4 then you arrive at (4,0) The cocksucker didn't reduce the fraction to simplest form. If you rise is -1 and your run is +2 and you start at (0,2) then you wind up at (2,1) and if you move one more increment to the next point on the line (rise -1, run +2) then you arrive at (4,0) Oh, and in my OP I entered my coordinates and the answer's coordinates backwards. My answer in the tool was (2,1) [which if 2x+4y=8 then 2(2)+4(1)=8] and that works out. That's all. The asshole programming the fucking answers into the computer didn't reduce the fraction for slope into simplest form. |
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Yep that was my line. I entered my coordinates in my post backwards, but in the test I entered them correctly. |
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Quoted:
I think the computer is wrong about 0,4. ETA: The correct x-intercept is 4,0 so either way you are wrong. Here's an online calculator that will do it http://www.coolmath.com/graphit/ Incorrect. 2x+4y=8 If I said that the coordinates were were (2,1) then 2(2)+4(1)=8 Which is true. The person who programmed the test didn't reduce the slope to simplest form. That is my only explanation. |
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Now I remember why I don't want to go back to school.  Ah it aint that bad. At least its not advanced calculus and Differential Equations. This is actually easy. I got a 100% on my first test and by Thursday I will be taking my second test. It has taken me 5 days to complete the chapter on functions and graphs. Unfortunately, I am going to get a Computer Science degree eventually (since I've been in the field for 13 years now) and I'll be taking math for the rest of my college career. |
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Quoted: Quoted: I think the computer is wrong about 0,4. ETA: The correct x-intercept is 4,0 so either way you are wrong. Here's an online calculator that will do it http://www.coolmath.com/graphit/ Incorrect. 2x+4y=8 If I said that the coordinates were were (2,1) then 2(2)+4(1)=8 Which is true. The person who programmed the test didn't reduce the slope to simplest form. That is my only explanation. There are an infinite number of solutions. (2,1) is just one of them. For example you could have put (2,1) and (6, -1) Both are solutions but not the x and y intercept. The only significant answers are the y and x intercepts, which are (0,2) and (4,0) |