khunsanuk Posted May 30, 2011 Report Share Posted May 30, 2011 Hi, I would have thought that Math of all school subjects would be the most similar between countries, but I might be wrong. I was taught formulas like this: 4x2 + 7x = 432 Our daughter is doing her homework on the PC at the moment and the formula on her screen reads: 4y2 - 9y + 55 And she has 2 fields below it: (+y)(-y) I honestly have no idea how you could solve that formula (there's no equation, so every value you can think of for y would work). I'm guessing the math is supposed to be the same, but the teaching method is totally different for sure. Sanuk! Link to comment Share on other sites More sharing options...
khunsanuk Posted May 30, 2011 Author Report Share Posted May 30, 2011 Hi, Having looked at her doing them, I get the impression that is actually "4y2 - 9y = +55" And both y's can have a different value. Still doesn't make much sense though, as I would think the y's should then both be a different letter. Oh well, maybe I am looking at this too logically Sanuk! Link to comment Share on other sites More sharing options...
Flashermac Posted May 30, 2011 Report Share Posted May 30, 2011 Yaw Yak and Yaw Ying? Link to comment Share on other sites More sharing options...
khunsanuk Posted May 30, 2011 Author Report Share Posted May 30, 2011 Hi, Hahahahaha, possibly Sanuk! Link to comment Share on other sites More sharing options...
Boo Radley Posted May 30, 2011 Report Share Posted May 30, 2011 4y2 - 9y = 55 This appears to be a quadratic equation. I never was very good at maths , but assuming it is, there are 2 values of y which will satisfy it, +5 and -2.75. You can substitute them in to prove it. When there are no simple factors for a quadratic equation of the form ax2 + bx+ c then the quadratic formula can be used:: x = -b +or- sqrt (b2-4ac)/2a. Using the quadratic formula for 4y2-9y-55=0 yields y=+5 or -2.75. Solution courtesy of my old Maths teacher Mr Knutsen from decades past. God bless his soul. There's a nice primer on quadratic equations here: http://www.education.gov.za/LinkClick.aspx?fileticket=QPRbNR%2F8peI%3D&tabid=621&mid=1735 [apologies if you'd got this far already!]. Link to comment Share on other sites More sharing options...
liquidflux Posted May 30, 2011 Report Share Posted May 30, 2011 Assuming that the 2 is squaring the y in the first term, then yes, you'd use the quadratic formula to solve. Link to comment Share on other sites More sharing options...
Redbaron Posted May 30, 2011 Report Share Posted May 30, 2011 assuming the 2 is squaring the y ... both y's equal 5 Link to comment Share on other sites More sharing options...
TheCorinthian Posted May 31, 2011 Report Share Posted May 31, 2011 If you can do this one: {first 10-digit prime in consecutive digits of 'e'} .com I will give you a job interview. Link to comment Share on other sites More sharing options...
TheCorinthian Posted May 31, 2011 Report Share Posted May 31, 2011 Oh, and then do this one: Imagine an analog clock set to 12 o'clock. Note that the hour and minute hands overlap. How many times each day do both the hour and minute hands overlap? How would you determine the exact times of the day that this occurs? Link to comment Share on other sites More sharing options...
expat Posted May 31, 2011 Report Share Posted May 31, 2011 Nice problems--give me more. Link to comment Share on other sites More sharing options...
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