Spec138 Posted April 13, 2011 Share Posted April 13, 2011 Really. You sure about that?I'd like you to solve the following equation for x 8x²/ 2x = 1 x=cube root of (1/4) Link to comment Share on other sites More sharing options...
dockeryfan Posted April 13, 2011 Share Posted April 13, 2011 I'd like you to solve the following equation for x 8x²/ 2x = 1 x=cube root of (1/4) lol, well you are probably the only person that would do that, because the rest of the world would solve that differently. In fact, I would hazard a guess that if you gave that to 100 mathematicians they would all reduce that to 4x=1 and x = 1/4 Link to comment Share on other sites More sharing options...
Spec138 Posted April 13, 2011 Share Posted April 13, 2011 I'd like you to solve the following equation for x8x²/ 2x = 1 lol, well you are probably the only person that would do that, because the rest of the world would solve that differently. In fact, I would hazard a guess that if you gave that to 100 mathematicians they would all reduce that to 4x=1 and x = 1/4 I would guess you'd be wrong because **technically** that's the correct answer. Fortunately for us, mathematicians don't use MS Word to discuss complex equations. This is a silly thread because it requires limits imposed on us by a very basic text editor. Link to comment Share on other sites More sharing options...
PokerPacker Posted April 13, 2011 Share Posted April 13, 2011 I would guess you'd be wrong because **technically** that's the correct answer. Fortunately for us, mathematicians don't use MS Word to discuss complex equations. This is a silly thread because it requires limits imposed on us by a very basic text editor. at least text editors actually have formula boxes you can insert (at least Open Office does). Link to comment Share on other sites More sharing options...
Spec138 Posted April 13, 2011 Share Posted April 13, 2011 at least text editors actually have formula boxes you can insert (at least Open Office does). Maybe notepad would have been a more appropriate comparison Link to comment Share on other sites More sharing options...
Thinking Skins Posted April 13, 2011 Share Posted April 13, 2011 This whole debate shows the purpose for parenthesis. Every equation has an extended form, but they're not always easy to read and interpret, hence the parenthesis. Since there are no parenthesis other than the (9+3), the answer is 288, but its a common enough mistake that that this is often on math tests and even confuses mathematicians in well published math journals - or on calculators. But the rules are the rules. Link to comment Share on other sites More sharing options...
truskinsfan18 Posted April 13, 2011 Share Posted April 13, 2011 Any math whiz out there who can help me with my math hw? What is the derivative of: 4(e^(-.2x)-e^(-3x)) I need to evaluate what the derivative of this function is at x=2 Link to comment Share on other sites More sharing options...
Mark The Homer Posted April 13, 2011 Share Posted April 13, 2011 This whole debate shows the purpose for parenthesis. Every equation has an extended form, but they're not always easy to read and interpret, hence the parenthesis. Since there are no parenthesis other than the (9+3), the answer is 288, but its a common enough mistake that that this is often on math tests and even confuses mathematicians in well published math journals - or on calculators. But the rules are the rules. You're right, of course. But as I've said before, mathematicians don't write equations that look like this. This is the equation of a sloppy writer or a trickster. ---------- Post added April-13th-2011 at 07:36 PM ---------- This whole debate shows the purpose for parenthesis. Every equation has an extended form, but they're not always easy to read and interpret, hence the parenthesis. Since there are no parenthesis other than the (9+3), the answer is 288, but its a common enough mistake that that this is often on math tests and even confuses mathematicians in well published math journals - or on calculators. But the rules are the rules. You're right, of course. But as I've said before, mathematicians don't write equations that look like this. This is the equation of a sloppy writer or a trickster. Link to comment Share on other sites More sharing options...
mikered30 Posted April 14, 2011 Share Posted April 14, 2011 WTF, it is almost 50/50. Who ever is trying to piss me off, it is working. Link to comment Share on other sites More sharing options...
Spec138 Posted April 14, 2011 Share Posted April 14, 2011 Any math whiz out there who can help me with my math hw? What is the derivative of: 4(e^(-.2x)-e^(-3x)) I need to evaluate what the derivative of this function is at x=2 d/dx(4 (e^(-0.2 x)-e^(-3 x))) = 12 e^(-3 x)-0.8 e^(-0.2 x) Haven't done derivatives in a while but wolfram is a life saver. Link to comment Share on other sites More sharing options...
Ancalagon the Black Posted April 14, 2011 Share Posted April 14, 2011 The thread is reaching new heights! I'm particularly amused by whoever it is defending the (correct) 288 answer by claiming that their opponent is doing calculus on an algebra problem. This isn't even an algebra problem - it's arithmetic! Link to comment Share on other sites More sharing options...
Thinking Skins Posted April 14, 2011 Share Posted April 14, 2011 You're right, of course. But as I've said before, mathematicians don't write equations that look like this. This is the equation of a sloppy writer or a trickster. Only on tests to trick little kids. Link to comment Share on other sites More sharing options...
PokerPacker Posted April 14, 2011 Share Posted April 14, 2011 Any math whiz out there who can help me with my math hw? What is the derivative of: 4(e^(-.2x)-e^(-3x)) I need to evaluate what the derivative of this function is at x=2 I do believe that would be: -.8e^-.2x + 12e^-3x derivative of e^ax = ae^ax Link to comment Share on other sites More sharing options...
RansomthePasserby Posted April 14, 2011 Share Posted April 14, 2011 50/50??? 50/50????????? Link to comment Share on other sites More sharing options...
SonOfWashington Posted April 14, 2011 Share Posted April 14, 2011 I do believe that would be: -.8e^-.2x + 12e^-3xderivative of e^ax = ae^ax THERE'S THEM LACK OF PARENTHESIS AGAIN. Though this is almost right. I got 4*(-.2e^(-.2x) + 3e^(-3x)), which distributes to -.8e^(-.2x) + 12e^(-3x), as Spec posted earlier. Obviously just plug in x=2 for that answer. Link to comment Share on other sites More sharing options...
PokerPacker Posted April 14, 2011 Share Posted April 14, 2011 THERE'S THEM LACK OF PARENTHESIS AGAIN.Though this is almost right. I got 4*(-.2e^(-.2x) + 3e^(-3x)), which distributes to -.8e^(-.2x) + 12e^(-3x), as Spec posted earlier. Obviously just plug in x=2 for that answer. bah humbug. Link to comment Share on other sites More sharing options...
Toe Jam Posted April 14, 2011 Share Posted April 14, 2011 50/50??? 50/50????????? It's not that shocking. Just shows half the people on ES are dumb dumbs and the other half are geniuses. I'd like to point out that more than likely most of the geniuses are liberals. :evilg: Link to comment Share on other sites More sharing options...
MVille_Skins Posted April 14, 2011 Share Posted April 14, 2011 This thread got way too serious and tempers flared. Time for some lulz on the matter at hand Link to comment Share on other sites More sharing options...
Pwyl Posted April 14, 2011 Share Posted April 14, 2011 no, I don't think so. I think if it were written 8x²/ 2x = 1 and 8x² ÷ 2x = 1 You could possibly make an argument that the second means this (8)(x²)(1/2)x = 1 with the whole order of operations argument But in my opinion the first one puts 2x in the denominator every time. Every time. That is what I am talking about and why " ÷ " is the culprit. Nope, wrong And I say that because most people who have ever used a computer or calculator that accepts in-line equation entering automatically rewrite x÷y to x/y. That's what I did with the original equation in this thread when I wrote it on paper to solve it, and was forced to do so to punch it into excel, because there isn't a ÷ key on my keyboard. (I also had to add a * for multiplication because programming languages[and by extension the pseudo-programming language of excel formulas] don't recognize 2(12) as multiplication at all). you can do a basic test of that notion by looking at (2 ÷ 2 + 2) vs (2 / 2 + 2). You don't automatically assume that 2+2 is in the denominator in either instance, because there's no structural reason to. When you contrast that with the other equation you posed, why do you assume that 2x is atomic (ie supposed to be read as (2x) )? I don't think it has anything to do with the division symbol, since like I said most people automatically transpose symbols even if they don't realize it. I think it's because the form of that equation gives you an algebraic notion that 2x is atomic. But I'm not even sure at this point what we're really disagreeing on, so maybe I should let it drop Link to comment Share on other sites More sharing options...
ATLredskin Posted April 14, 2011 Share Posted April 14, 2011 It's order of operations.With that said, again, you add the 9+3 since they're in parentheses. That's 12. There are no more parentheses. You're equation now looks like this: 48+2(12). Then, you do division/multiplication from left to right which means you divide the 48 by 2 and get 24. That leaves you with 24(12) which is 288. You're welcome. I won't even charge for this tutoring session. How are you going to say there is no more parentheses, but in the same sentence you present the same problem with parentheses in it. Just because you add 9+3 doesn't mean you got rid of the parentheses. You get rid of it by multiplying 12 by 2 which will give you 24....divide and you will get 2!!! Link to comment Share on other sites More sharing options...
Pwyl Posted April 14, 2011 Share Posted April 14, 2011 How are you going to say there is no more parentheses, but in the same sentence you present the same problem with parentheses in it. Just because you add 9+3 doesn't mean you got rid of the parentheses. You get rid of it by multiplying 12 by 2 which will give you 24....divide and you will get 2!!! Except that's not what order of operations says. Order of operations says to evaluate the expression INSIDE the parentheses. parentheses allow for explicit grouping, which they ENCLOSE. Once you evaluate 9+3, the explicit grouping represented by the parentheses is gone. You're subconciously adding a second set of parentheses around 2*12, which aren't explicitly written in this equation. If you have a reason to do that, like you might with the equation DF posted, you would be right. But straight-up arithmetic order of operations says the explicit grouping represented by the parens is satisified once you evaluate the expression inside them, and you're on to the MD step of evaluation. Link to comment Share on other sites More sharing options...
dockeryfan Posted April 14, 2011 Share Posted April 14, 2011 Nope, wrong And I say that because most people who have ever used a computer or calculator that accepts in-line equation entering automatically rewrite x÷y to x/y. Well, you better tell this guy that he's solving the problem incorrectly. Q.1 2 divided by (2/x + 2/y)(2/x + 2/y) = 2 (1/x + 1/y) = 2 ( (y + x)/xy) (I solved 1/x + 1/y by finding common denominator xy and then multiplying the numerator by x and y respectively) = 2(y+x)/xy Now we have to solve 2 divided by 2(y + x)/xy we get 2 xy/2(y + x) = xy/(y + x) http://www.algebra.com/algebra/homework/Polynomials-and-rational-expressions/Polynomials-and-rational-expressions.faq.question.54286.html because OBVIOUSLY, as you say, if you take (y+x)/xy you should get (y+x)(1/x)(y). I mean it's clear as day to you, why isn't it clear as day to this guy? He must be an idiot. He clearly does not understand order of operations. Look. I understand the answer is 288. I know this because of the divisor symbol. But saying that every math guy out there would take 8x^2/2x = 1 and come up with x=cube root of 1/4 is idiotic. They would not. And all you have to do is go to one of those tutor websites and put in a question and they'll all get it wrong I guarantee it. Ask them a stupid question like how do I reduce 24x/8x and I would bet they all come up with 3. Not 3x^2 Link to comment Share on other sites More sharing options...
Stadium-Armory Posted April 14, 2011 Share Posted April 14, 2011 http://www.youtube.com/watch?v=D8kVqjUO92c&feature=relatedhttp://www.youtube.com/watch?v=D8kVqjUO92c&feature=related Link to comment Share on other sites More sharing options...
Forehead Posted April 14, 2011 Share Posted April 14, 2011 This has gone on for 42 pages and half the people have answered wrong. I weep for this board, for education, and for humanity. Link to comment Share on other sites More sharing options...
RansomthePasserby Posted April 14, 2011 Share Posted April 14, 2011 This has gone on for 42 pages and half the people have answered wrong. I weep for this board, for education, and for humanity. Meh, it's really not all that bad. This would all be cleared up if the original problem was more explicit. Just goes to show why, if you want something done right, you have to communicate clearly. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.