Math problem -- help/hints please (NOW SOLVED: includes solution)
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Okay, so I've dug out my old A-level maths text to try and brush up on my skills. I've managed to struggle through the 1st chapter and associated exercises but have one question that I've got wrong and I can't for the life of me figure out where I'm going wrong. So, if any of you guys can help point me in the right direction I'd be really grateful: So I have the following I need to solve for x: (x-4)/6 - 2x+1 = (3x-4)/2 My approach was to find the lcm, which is 6 and then do this: 1(x-4) - 6(2x+1) = 3(3x-4) multiply out the brackets: x-4 - 12x-6 = 9x-12 which yields: 20x = 2 or x = 1/10 However, the back of the book says I'm wrong. It's really bugging me - I feel I'm falling at first step as I'm pretty confident once I've removed the fractional component that I'm doing everything correctly. Thanks guys, Kev Correct Solution follows: (x-4)/6 - 2x+1 = (3x-4)/2 lcm is 6 so multiply out the terms: 1(x-4) + 6(-2x+1) = 3(3x-4)/2 => This is where I'd gone wrong 6(-2x+1) multiplying out: x -4 -12x +6 = 9x -12 -4 +6 +12 = 9x -x +12x 14=20x x=14/20 or 7/10 YAY!
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Okay, so I've dug out my old A-level maths text to try and brush up on my skills. I've managed to struggle through the 1st chapter and associated exercises but have one question that I've got wrong and I can't for the life of me figure out where I'm going wrong. So, if any of you guys can help point me in the right direction I'd be really grateful: So I have the following I need to solve for x: (x-4)/6 - 2x+1 = (3x-4)/2 My approach was to find the lcm, which is 6 and then do this: 1(x-4) - 6(2x+1) = 3(3x-4) multiply out the brackets: x-4 - 12x-6 = 9x-12 which yields: 20x = 2 or x = 1/10 However, the back of the book says I'm wrong. It's really bugging me - I feel I'm falling at first step as I'm pretty confident once I've removed the fractional component that I'm doing everything correctly. Thanks guys, Kev Correct Solution follows: (x-4)/6 - 2x+1 = (3x-4)/2 lcm is 6 so multiply out the terms: 1(x-4) + 6(-2x+1) = 3(3x-4)/2 => This is where I'd gone wrong 6(-2x+1) multiplying out: x -4 -12x +6 = 9x -12 -4 +6 +12 = 9x -x +12x 14=20x x=14/20 or 7/10 YAY!
Other people have pointed this out already (so I'm not going to take the credit for solving this), but trying to stick to your calculations as closely as possible:
(x-4)/6 - 2x+1 = (3x-4)/2
My approach was to find the lcm, which is 6 and then do this:
1(x-4) - 6(2x-1) = 3(3x-4) <-- note 2x-1, not 2x+1 because previous line is -2x + 1, not - (2x + 1)
multiply out the brackets:
x-4 - 12x+6 = 9x-12 <-- from previous line 12x+6, not 12x-6
which yields:
20x = 14
or x = 7/10Jon CodeWrite
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You're slipping. I used a spreadsheet and brute forced it by checking every fraction from 0.1 to 3.0
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Okay, so I've dug out my old A-level maths text to try and brush up on my skills. I've managed to struggle through the 1st chapter and associated exercises but have one question that I've got wrong and I can't for the life of me figure out where I'm going wrong. So, if any of you guys can help point me in the right direction I'd be really grateful: So I have the following I need to solve for x: (x-4)/6 - 2x+1 = (3x-4)/2 My approach was to find the lcm, which is 6 and then do this: 1(x-4) - 6(2x+1) = 3(3x-4) multiply out the brackets: x-4 - 12x-6 = 9x-12 which yields: 20x = 2 or x = 1/10 However, the back of the book says I'm wrong. It's really bugging me - I feel I'm falling at first step as I'm pretty confident once I've removed the fractional component that I'm doing everything correctly. Thanks guys, Kev Correct Solution follows: (x-4)/6 - 2x+1 = (3x-4)/2 lcm is 6 so multiply out the terms: 1(x-4) + 6(-2x+1) = 3(3x-4)/2 => This is where I'd gone wrong 6(-2x+1) multiplying out: x -4 -12x +6 = 9x -12 -4 +6 +12 = 9x -x +12x 14=20x x=14/20 or 7/10 YAY!
You dropped a sign in your third step: (x - 4) / 6 - 2x + 1 = (3x - 4) / 2 (x - 4) - 6(2x + 1) = 3(3x - 4) (x - 4) - 12x + 6 = 3(3x - 4) x - 4 - 12x + 6 = 9x - 12 -11x + 2 = 9x - 12 -20x = -14 x = 7 / 10
"Seize the day" - Horace "It's not what he doesn't know that scares me; it's what he knows for sure that just ain't so!" - Will Rogers, said by him about Herbert Hoover
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I can tell you the answer is 7/10 but not because I can remember how to solve this from A-Level maths, but because I long ago realised such things are futile, and excel can solve this much quicker than I can.
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Bang on (although the 'book answer' is 7/10 - simplest fractional answer). I'm curious about your notation though, what's with the factorial -1?
LOL, cool, that's the answer I got. Those mangled signs will get you every time.
"Seize the day" - Horace "It's not what he doesn't know that scares me; it's what he knows for sure that just ain't so!" - Will Rogers, said by him about Herbert Hoover
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Okay, so I've dug out my old A-level maths text to try and brush up on my skills. I've managed to struggle through the 1st chapter and associated exercises but have one question that I've got wrong and I can't for the life of me figure out where I'm going wrong. So, if any of you guys can help point me in the right direction I'd be really grateful: So I have the following I need to solve for x: (x-4)/6 - 2x+1 = (3x-4)/2 My approach was to find the lcm, which is 6 and then do this: 1(x-4) - 6(2x+1) = 3(3x-4) multiply out the brackets: x-4 - 12x-6 = 9x-12 which yields: 20x = 2 or x = 1/10 However, the back of the book says I'm wrong. It's really bugging me - I feel I'm falling at first step as I'm pretty confident once I've removed the fractional component that I'm doing everything correctly. Thanks guys, Kev Correct Solution follows: (x-4)/6 - 2x+1 = (3x-4)/2 lcm is 6 so multiply out the terms: 1(x-4) + 6(-2x+1) = 3(3x-4)/2 => This is where I'd gone wrong 6(-2x+1) multiplying out: x -4 -12x +6 = 9x -12 -4 +6 +12 = 9x -x +12x 14=20x x=14/20 or 7/10 YAY!
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Yes I have - and I learned something about CHECKING the bloody signs!! :-D Thanks guys - I can now confidently move onto the next chapter knowing I'm not missing something critical! This is the first time I've used CodeProject this way and I'm well impressed by the generosity of you guys.. :thumbsup:
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J4amieC wrote:
excel can solve this much quicker than I can
Have become a manager?
"Fear no factor", Prime Numbers.
d@nish wrote:
Have become a manager?
If I had turned into a manager I would be using Project to organise people to document the problem, an architect to design the proper implementation to solve the solution, developers to develop the solution and testers to provide automated testing that the solution fulfils the requirements. A smart person like me just plugged the 2 sides of the equation into a goalseak in Excel and came out with a solution in about 30 seconds.
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d@nish wrote:
Have become a manager?
If I had turned into a manager I would be using Project to organise people to document the problem, an architect to design the proper implementation to solve the solution, developers to develop the solution and testers to provide automated testing that the solution fulfils the requirements. A smart person like me just plugged the 2 sides of the equation into a goalseak in Excel and came out with a solution in about 30 seconds.
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Okay, so I've dug out my old A-level maths text to try and brush up on my skills. I've managed to struggle through the 1st chapter and associated exercises but have one question that I've got wrong and I can't for the life of me figure out where I'm going wrong. So, if any of you guys can help point me in the right direction I'd be really grateful: So I have the following I need to solve for x: (x-4)/6 - 2x+1 = (3x-4)/2 My approach was to find the lcm, which is 6 and then do this: 1(x-4) - 6(2x+1) = 3(3x-4) multiply out the brackets: x-4 - 12x-6 = 9x-12 which yields: 20x = 2 or x = 1/10 However, the back of the book says I'm wrong. It's really bugging me - I feel I'm falling at first step as I'm pretty confident once I've removed the fractional component that I'm doing everything correctly. Thanks guys, Kev Correct Solution follows: (x-4)/6 - 2x+1 = (3x-4)/2 lcm is 6 so multiply out the terms: 1(x-4) + 6(-2x+1) = 3(3x-4)/2 => This is where I'd gone wrong 6(-2x+1) multiplying out: x -4 -12x +6 = 9x -12 -4 +6 +12 = 9x -x +12x 14=20x x=14/20 or 7/10 YAY!
x=7/10
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x=7/10
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Of course!! Thanks buddy! :-)
You're welcome! :-D
"With sufficient thrust, pigs fly just fine."
Ross Callon, The Twelve Networking Truths, RFC1925
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x=7/10