Nakor
Star
Non-Prophet
Posts: 991
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Post by Nakor on Apr 20, 2010 20:05:53 GMT -5
Hmm, missed the relatively prime integers bit in the question. Doh. Been too long. Still, I think that makes the answer 52, not 13.
Start with: y=-2.5x+26
Multiply both sides by 2 to remove decimals: 2y=-5x+52
Add 5x to both sides: 5x+2y=52
A=5, B=2, C=52.
According to your answer of (3,2,13):
3x+2y=13
2y=-3x+13
y=-1.5x+6.5 --- this isn't perpendicular to y=0.4x-3 nor does it intersect point (10,1).
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TheIslander
Planet
From a Land Surrounded by Sea.
Posts: 403
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Post by TheIslander on Apr 20, 2010 22:04:34 GMT -5
Hmm, missed the relatively prime integers bit in the question. Doh. Been too long. Still, I think that makes the answer 52, not 13. Start with: y=-2.5x+26 Multiply both sides by 2 to remove decimals: 2y=-5x+52 Add 5x to both sides: 5x+2y=52 A=5, B=2, C=52. According to your answer of (3,2,13): 3x+2y=13 2y=-3x+13 y=-1.5x+6.5 --- this isn't perpendicular to y=0.4x-3 nor does it intersect point (10,1). I accidentally divided instead of multiplied at C (ugh! ZzZ) so you are right, C=52... I also messed up with the 2.5 thinking its 3/2 rather than 5/2. what you are saying is completely right. eq of normal/perpendicular: 2y = -5x + 52 Edited my first post, there should be everything needed there to solve it. ps. I was always thought to deal with fractions rather than decimals in algebra... it makes things so much easier. Especially in coord geometry for example in this problem y = -5/2 + 26 .. the 1/2 in 5/2 was just crying out to be taken as common and multiplied on both sides. I dont get how people work with decimals. I just got confused since i was typing in decimals. Decimals = evil  |
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Nakor
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Non-Prophet
Posts: 991
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Post by Nakor on Apr 20, 2010 22:23:23 GMT -5
Decimals and fractions are really a personal preference thing. The reason I prefer decimals in many situations is that it reduces the total number of coefficients that you're dealing with (5/2 has two coefficients while 2.5 is a single coefficient), making things a bit quicker to simplify.
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bry4nmw
Meteorite
Live. Laugh. Learn. Love.
Posts: 6
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Post by bry4nmw on Apr 21, 2010 0:18:23 GMT -5
TheIslander I am positive your solution is right though in when I solved it I skipped a lot of the steps you took. Nakor you need to double your equation of 2.5x + 1y = 26 because it asks for integer values. And thats why the equation ends up 5x + 2y = 52. So overall I conclude that C = 52 EDIT: Ops didn't see the 2nd page.
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Post by Ryan on Apr 21, 2010 0:28:12 GMT -5
So, can anyone tell me if the subset of nilpotent elements of a ring forms a subring?
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