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 10-10-08, 07:42 PM #1 Tom Stormcrowe Out fishing with Annie on his lap, a cigar in one hand and a ginger ale in the other, watching the sunset. Thread Starter     Join Date: Mar 2006 Location: South Florida Bikes: Techna Wheelchair and a Sun EZ 3 Recumbent Trike Posts: 16,128 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Where am I going wrong? Math) I can't figure out where I'm going wrong on this.....help please! Points A(5,0), B(-1,4) a find slope first M AB=(4-0)/(-1-5)=4/-6, so m=-2/3 y=mx+b y=-2/3x+4 The school server says the correct answer is y=-2/3x+10/3...... I thought I knew this stuff __________________ . “He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you.”- Fredrick Nietzsche "We can judge the heart of a man by his treatment of animals." - Immanuel Kant
 10-10-08, 08:07 PM #2 thomson Senior Member     Join Date: Dec 2003 Bikes: Posts: 3,332 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) b is the y intercept, that is the y point where the line crosses the y axis. It is not the difference in y values from two arbitrary points. __________________
10-10-08, 08:31 PM   #3
KingTermite
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b is the y intercept. Once you have the slope, you can plug either point back in and solve for b.

In the first case:
0 = -2/3(5) + b
0 = -10/3 + b
b=10/3

Use other point to get same result
4 = -2/3(-1) + b
4 - 2/3 = b
12/3 - 2/3 = b
10/3 = b

Either way, you get same y-intercept, so answer is y=-2/3x + 10/3
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10-10-08, 08:33 PM   #4
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As a visual guide, here is a graph. Above 3, but clearly below 4.

KingTermite beat me to it regarding the math.
Attached Images
 -2-thirds.JPG (4.5 KB, 2 views)

 10-10-08, 08:38 PM #5 Tom Stormcrowe Out fishing with Annie on his lap, a cigar in one hand and a ginger ale in the other, watching the sunset. Thread Starter     Join Date: Mar 2006 Location: South Florida Bikes: Techna Wheelchair and a Sun EZ 3 Recumbent Trike Posts: 16,128 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Thanks, I needed a refresher, I guess, as I haven't had to mess with this for a few years. __________________ . “He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you.”- Fredrick Nietzsche "We can judge the heart of a man by his treatment of animals." - Immanuel Kant
 10-10-08, 08:45 PM #6 thomson Senior Member     Join Date: Dec 2003 Bikes: Posts: 3,332 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) I thought we weren't supposed to give the answer __________________
 10-10-08, 08:49 PM #7 jschen riding once again     Join Date: Oct 2005 Location: San Diego, CA Bikes: '06 Cervelo R3, '05 Specialized Allez Posts: 7,359 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Also, check your equation against the original inputs, and you can clearly see that your equation is wrong. __________________ If you notice this notice then you will notice that this notice is not worth noticing.
 10-10-08, 09:09 PM #8 Tom Stormcrowe Out fishing with Annie on his lap, a cigar in one hand and a ginger ale in the other, watching the sunset. Thread Starter     Join Date: Mar 2006 Location: South Florida Bikes: Techna Wheelchair and a Sun EZ 3 Recumbent Trike Posts: 16,128 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Yeah, I was just getting stressed out and frustrated. Not a good combination, if you know what I mean. Forest/trees issue. It was all blurring together in frustration. __________________ . “He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you.”- Fredrick Nietzsche "We can judge the heart of a man by his treatment of animals." - Immanuel Kant
 10-10-08, 09:11 PM #9 jschen riding once again     Join Date: Oct 2005 Location: San Diego, CA Bikes: '06 Cervelo R3, '05 Specialized Allez Posts: 7,359 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) No, not a forest/trees issue. Math is not subject to interpretation. One needs to make sure one's fundamental concepts are rock solid and go from there. __________________ If you notice this notice then you will notice that this notice is not worth noticing.
10-10-08, 09:15 PM   #10
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Math! On a Friday night!

Jeeze ...
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 10-10-08, 09:41 PM #11 deraltekluge Senior Member     Join Date: Sep 2006 Bikes: Kona Cinder Cone, Sun EZ-3 AX Posts: 1,195 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) How are you with solving systems of simultaneous equations? Here's another way of looking at the problem: You want to write an equation of the form y = mx + b You have two sets of values for x and y that will satisfy the equation...plug each set into the equation and get a system of two equations for m and b. 0 = 5m + b 4 = -m + b Now, solve for m and b.
10-10-08, 10:04 PM   #12
Tom Stormcrowe
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Actually, it was, because I had gotten so frustrated I wasn't thinking straight and couldn't even see a glaring error. I took a break, chilled out and went through the rest of the problems with no issues. I'm extremely right brain dominant, and have always had issues with math.

Quote:
 Originally Posted by jschen No, not a forest/trees issue. Math is not subject to interpretation. One needs to make sure one's fundamental concepts are rock solid and go from there.
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. “He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you.”- Fredrick Nietzsche

"We can judge the heart of a man by his treatment of animals." - Immanuel Kant