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Terribad Math Skills!
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xLethargicax
United States469 Posts
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Navi
5286 Posts
you want to find the n'th term (10th in this case). In geometric sequence, to get the next term you multiply by r. so a1 = 200, a2 = -100 ... etc. do that to a10 baby and you're set. when i saw "math" in the title i thought this would be some dissertation level shit.... so many math dudes on here | ||
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xLethargicax
United States469 Posts
an'th = a1 * r ^ n-1 I am having trouble with the mechanical parts of it. How do I go about raising -1/2 to the 9th power? | ||
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coltrane
Chile988 Posts
On May 20 2010 09:47 Navi wrote: So, a1 is the first term of the geometric sequence. you want to find the n'th term (10th in this case). In geometric sequence, to get the next term you multiply by r. so a1 = 200, a2 = -100 ... etc. do that to a10 baby and you're set. when i saw "math" in the title i thought this would be some dissertation level shit.... so many math dudes on here just wanted to add that r stands for ratio, and n is usually used to design a natural number, like the n-th number in the sequence. And you can go to the 9th potence by doing it manually... thats how you study maths. When you get it... then start thinking about formulae. | ||
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s h 1 k 4 i
United States21 Posts
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love1another
United States1844 Posts
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dangots0ul
United States919 Posts
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Djzapz
Canada10681 Posts
A truck is on the highway at a constant speed of "s" km/h. The truck's gas consumption is shown by: q(s)= 1/250*((50/v)+v) in litres/km. The driver is paid $35/hour. Find at which speed the cost is at the minimum for the employer for a 254 kilometers drive provided that gasoline costs $1,059 per litre. It had me confused for a while but it was cewl =D PS: I'm horrible at math so it took me longer than it should have. | ||
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xLethargicax
United States469 Posts
I flipped the fraction over and did 2^9th = 512 but its over -1 so -512 + 200 = -312 so a10= -312 correct? | ||
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mmp
United States2130 Posts
On May 20 2010 09:58 dangots0ul wrote: don't worry bro, you won't be using 99% of this stuff ever after school. unless u go into math Or any field that involves thinking or rational planning or managing a budget... it's not a difficult problem so you should pay attention. Everything you learn in school can become important later on, even the boring stuff you may have no interest in. You don't want to grow up to be a dummy. | ||
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s h 1 k 4 i
United States21 Posts
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coltrane
Chile988 Posts
On May 20 2010 09:59 xLethargicax wrote: Thanks for all the help guys! So I believe the answer is a10=-312 right? I flipped the fraction over and did 2^9th = 512 but its over -1 so -512 + 200 = -312 so a10= -312 correct? so, are you trolling? No, look, you have 200 * (-1/2) = -100 200 * (1/4) = 25 200 * (-1/8) = 12.5 . . . So I dont get how could it be -312 And probably you wanna express that as a rational. | ||
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coltrane
Chile988 Posts
On May 20 2010 09:58 dangots0ul wrote: don't worry bro, you won't be using 99% of this stuff ever after school. unless u go into math Sorry for the double post, but whoever listen this douchebag is a douchebag aswell. And even if he is right, that 1% totally owns. | ||
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xLethargicax
United States469 Posts
On May 20 2010 10:05 coltrane wrote: so, are you trolling? No, look, you have 200 * (-1/2) = -100 200 * (1/4) = 25 200 * (-1/8) = 12.5 . . . So I dont get how could it be -312 And probably you wanna express that as a rational. I'm not trolling, I am just really struggling through math right now. Geometry and the beginning of this year was no problem. I just really really messed my algebra 1 up and now I am really behind in algebra 2. So if you follow each exponent eventually you get 200 * (-1/512) = but I am getting some crazy number...? .390? | ||
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s h 1 k 4 i
United States21 Posts
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Sadistx
Zimbabwe5568 Posts
On May 20 2010 09:59 Djzapz wrote: Since this is solved, I have a fun one (it was for me!) A truck is on the highway at a constant speed of "s" km/h. The truck's gas consumption is shown by: q(s)= 1/250*((50/v)+v) in litres/km. The driver is paid $35/hour. Find at which speed the cost is at the minimum for the employer for a 254 kilometers drive provided that gasoline costs $1,059 per litre. It had me confused for a while but it was cewl =D PS: I'm horrible at math so it took me longer than it should have. Take the derivative and find the minimum of the function? | ||
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Ravloo
United States145 Posts
On May 20 2010 10:15 xLethargicax wrote: So if you follow each exponent eventually you get 200 * (-1/512) = but I am getting some crazy number...? .390? Yeah, that's basically right Lethargicax. Just some extra to check your understanding: - The product is negative, since a positive*negative is negative (so should be -.390) - Also .390 is an approximation, not the exact answer. (ex: 1.99 is approximately 2). The exact using a calculator is -.390625 - If you DID round it you would round to -.391 since the next decimal place is a 6 Also it might help to see in fraction form and reducing: 200*(-1/512) = -200/512 = -25/64 (Just keep dividing top and bottom by two to reduce). And nice job on taking initiative to understand what's going on, stay motivated homie : ) | ||
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coltrane
Chile988 Posts
Its exactly 200 * (-1/512), so just write down -200/512, its ok, trust me. Or just ask a machine and write it. The important thing is that you get how it is done, and what does it mean, so you will be able to solve any problem like this one in the future, given any a_1, any r and any n. | ||
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xLethargicax
United States469 Posts
thanks a ton! | ||
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dangots0ul
United States919 Posts
On May 20 2010 10:08 coltrane wrote: Sorry for the double post, but whoever listen this douchebag is a douchebag aswell. And even if he is right, that 1% totally owns. great logic douchebag. | ||
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coltrane
Chile988 Posts
On May 20 2010 09:59 Djzapz wrote: Since this is solved, I have a fun one (it was for me!) A truck is on the highway at a constant speed of "s" km/h. The truck's gas consumption is shown by: q(s)= 1/250*((50/v)+v) in litres/km. The driver is paid $35/hour. Find at which speed the cost is at the minimum for the employer for a 254 kilometers drive provided that gasoline costs $1,059 per litre. It had me confused for a while but it was cewl =D PS: I'm horrible at math so it took me longer than it should have. that problem is horrible... have you ever thought about the driver's family? or about his rights as a worker? How many hours in a row you want your drivier driving?, have any fkn mba any idea on safety? This is no math, sir, this is pure explotation. edit:  603 shitty oneliners, nothing else to add... | ||
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Djzapz
Canada10681 Posts
On May 20 2010 10:25 Sadistx wrote: Take the derivative and find the minimum of the function? Yeah but you have to find the actual function which is the fun part =D | ||
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Mortality
United States4790 Posts
On May 20 2010 09:47 Navi wrote: when i saw "math" in the title i thought this would be some dissertation level shit.... so many math dudes on here Two things... 1. He did say "terribad" in the title.  2. I've never seen anything close to dissertation level here. | ||
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dangots0ul
United States919 Posts
On May 20 2010 10:37 coltrane wrote: that problem is horrible... have you ever thought about the driver's family? or about his rights as a worker? How many hours in a row you want your drivier driving?, have any fkn mba any idea on safety? This is no math, sir, this is pure explotation. edit: 603 shitty oneliners, nothing else to add...clearly some one doesn't know how to go through post history. Its ok, logical reasoning is not for everyone. Someone has got to be the kid sitting in the back with the helmets and seat belts | ||
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Kwidowmaker
Canada978 Posts
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coltrane
Chile988 Posts
On May 20 2010 12:52 dangots0ul wrote: clearly some one doesn't know how to go through post history. Its ok, logical reasoning is not for everyone. Someone has got to be the kid sitting in the back with the helmets and seat belts because when I click profile in the upper right corner of your post, and then click the number of posts I dont find 600 one liners about bleach manga... Please stay, you are so usefull to the site. I love to have you around. | ||
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SpiritoftheTunA
United States20903 Posts
On May 20 2010 15:05 Kwidowmaker wrote: This kept me up a bit last night. If a and b are positive integers, prove that sqrt(a) + sqrt(b) is rational if and only if a and b are perfect squares well you need only two pieces, the fact that the square root of any integer that isnt a perfect square is irrational, and that anything added to an irrational number is still irrational so conversely, it's rational only if both terms are square roots of perfect squares i dont know any algebraic or formal proofs though | ||
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dangots0ul
United States919 Posts
On May 20 2010 22:16 coltrane wrote: because when I click profile in the upper right corner of your post, and then click the number of posts I dont find 600 one liners about bleach manga... Please stay, you are so usefull to the site. I love to have you around. 15 / 600 definitely = 600 one liners. clap clap for the special kid! | ||
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nineninja9
United States194 Posts
On May 21 2010 02:28 SpiritoftheTunA wrote: well you need only two pieces, the fact that the square root of any integer that isnt a perfect square is irrational, and that anything added to an irrational number is still irrational so conversely, it's rational only if both terms are square roots of perfect squares i dont know any algebraic or formal proofs though That's not actually true. Two irrational numbers added together can in fact be rational. | ||
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FiBsTeR
United States415 Posts
On May 21 2010 02:28 SpiritoftheTunA wrote: well you need only two pieces, the fact that the square root of any integer that isnt a perfect square is irrational, and that anything added to an irrational number is still irrational That second thing isn't true: sqrt(2) and -sqrt(2) are both irrational but their sum is 0, which is rational. Rational + rational = rational, rational * rational = rational, rational + irrational = irrational, rational * irrational = irrational, but you can't say anything about irrational + irrational or irrational * irrational. + Show Spoiler + Suppose b is not a perfect square, so that sqrt(b) is irrational. If sqrt(a) + sqrt(b) is rational, then (sqrt(a) + sqrt(b)) - 2sqrt(b) = sqrt(a) - sqrt(b) is irrational. Multiplying these gives a - b, which must be irrational, which can't be if a, b are positive integers. So b is a perfect square, and the result follows from symmetry. EDIT: ninja'd by nineninja :o On May 20 2010 10:08 coltrane wrote: Sorry for the double post, but whoever listen this douchebag is a douchebag aswell. And even if he is right, that 1% totally owns. LOL this is so clever, I'm stealing this. I hear that "math is 99% useless" phrase so much, this is perfect.  | ||
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s h 1 k 4 i
United States21 Posts
Could you also say the following? Since Q is a field, sqrt(a) + sqrt(b) rational implies that if either sqrt(a) or sqrt(b) is rational, then the other must be rational (by closure under addition). Thus, if the statement isn't true, then they both must be irrational. Then use the fact that two strictly positive irrational numbers can never sum to a rational. | ||
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semantics
10040 Posts
plug problems into there and use show steps =p low level math can all be done and steps shown on wolfram i wish i had this when i was going though algebra and calc. | ||
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Nytefish
United Kingdom4282 Posts
On May 21 2010 06:40 semantics wrote: http://www.wolframalpha.com/ plug problems into there and use show steps =p low level math can all be done and steps shown on wolfram i wish i had this when i was going though algebra and calc. Haha I use it for uni level maths sometimes Well low level but messy stuff like algebra or series expansions that you want to quickly check you got right. | ||
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FiBsTeR
United States415 Posts
On May 21 2010 06:30 s h 1 k 4 i wrote: Since Q is a field, sqrt(a) + sqrt(b) rational implies that if either sqrt(a) or sqrt(b) is rational, then the other must be rational (by closure under addition). Thus, if the statement isn't true, then they both must be irrational. Then use the fact that two strictly positive irrational numbers can never sum to a rational. Sorry, that doesn't work either. I used the closure of Q over addition and multiplication in my proof, I just didn't explicitly state it. But two strictly positive irrationals can still sum to a rational. Take sqrt(2) and 2 - sqrt(2). | ||
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s h 1 k 4 i
United States21 Posts
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