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  1. Sirius Black

    linear algrebra question

    Consider the vector space R3. Find four vectors a, a',b,b' such that A=Sp{a,a'} B=Sp{b,b'} and A+B=R3 and AnB(A intesects B)=Sp{(1,1,1)} does anyone know how to make two planes into a space i.e. R3...
  2. Sirius Black

    math tutor in penrith needed !!!

    hey hav u got a math tutor yet? if not, PM me^^
  3. Sirius Black

    Any suggestion on related text?

    I didn't study documentary narrative for my HSC~ so my suggestion would be very general: -choose different genres of texts eg. u can choose a cartoon for ur related material -choose different aspects of journey eg. if the stolen children mostly talks about physical journey(I didn't study this...
  4. Sirius Black

    Help.... > _ <

    u should look through the adv&standard forums~ they've got heaps there^^ btw @ Survivor: we should have one section for general techniques too in ESL forum hehe~
  5. Sirius Black


    The 4-digit number 2652 is such that anyu two consecutive digits from it make a multiple of 13. Another number N has the same property but with 100 digits, and begins with 9. what is the last digit of N? choices: (a)2 (b)3 (c)6 (d) 9 N= 913913913.... SO the answer is d? thanx in advance:)
  6. Sirius Black

    could any1 help on this plz

    hehe,ur reasoning sounds a bit like fudging... can u elaborate on that ? If u take time to expand the RHS of the given formula, u can derive an expression in the form of LHS i.e. the result given in the question in NOT wrong. this can be further simplifed to +/-√7 +/-√3
  7. Sirius Black

    could any1 help on this plz

    NO could anyone help plz?
  8. Sirius Black

    could any1 help on this plz

    but the problem is that if u use the substituition given in the question u will get two sets of results :rolleyes: as A=2b-a<sup>2</sup> and B=b<sup>2</sup> if B=16 as in the question, u can hav b=+/-4 right? my question is that why the given result doesn't hold when b=-4 (LHS=/=RHS as u said)
  9. Sirius Black

    could any1 help on this plz

    If you factorise x<sup>4</sup>-20x<sup>2</sup>+16=(x<sup>2</sup>+4x-4)(x<sup>2</sup>-4x-4) OR=(x<sup>2</sup>+2sqrt7 x+4)(x<sup>2</sup>-2sqrt7 x+4) by using the result of x<sup>4</sup>+Ax<sup>2</sup>+B=(x<sup>2</sup>+ax+b)(x<sup>2</sup>-ax+b) but the 4 roots to...
  10. Sirius Black

    guess ur raw mark

    vitually no one. Last year one Korean oversea student got 98, but that was aligned mark. My phys teacher told me among all papers he's marked, only one person got raw mark of 92 in 1990s for phys and that was the top mark in the state...
  11. Sirius Black

    help on Q4 + Q15 in phys specimen paper

    In the solution provided by Success One Book Q4-A Why isn't the hammer experiencing centripedal acceleration towards the center of the Earth when its dropped from geosychronous orbit as in (B)? Q15-D Doesn't radio wave always travel at C regardless of medium? if so, if the frequency is the...
  12. Sirius Black

    Dreamerish*~'s Guide to Water Monitoring and Management

    thanks for ur notes 1.Electrical conductivity can be used to measure the concentration of dissolved salts present as ions, called salinity. The units are microsiemens per centimetre (µS cm-1). Because ionic compounds conduct electricity in solution, the more dissolved salts (ions), the higher...
  13. Sirius Black

    2003 HSC Q17 (c)

    could any1 explain the trends in the graph plz (in particular the peak) thanx
  14. Sirius Black

    Quantitative Analysis for Rust

    In this case, the missing mass is the rust? our teacher actually made the water evaporised and then reweighed. btw, in this option, are we supposed to know the quantitative analysis for rust ??
  15. Sirius Black

    help on production of polyethylene

    Part 1 of syllabus says that " outline teh steps in the production of polyethylene as an example of acommercially andindsutrially important polymer" Is there any difference between commericial and industrial methods to produce polyethylene? :rolleyes: thanx a lot
  16. Sirius Black


    I went throught the Comments from examiners for 2003 HSC and it says most responses refer to "ethanol, cellulose, ethene" for the question. The first two is right. but how could ethene become biomass?
  17. Sirius Black

    Chinese background speakers

    haha i did talk about the techniques coz the question asks for "how... relate to the global issues?" ( i think the examiners have no ideas about the intertextuality of these texts ...) i didnt know that 蚊烟 either,our Chinese teacher never discussed that symbolism before. Overall, i think its...
  18. Sirius Black

    two confusing dot points

    Isn't this prac all about electrolysis rather than CORROSION? also got another question- why is salt water results in higher rate of corrosion than acidic solution? (I know in low pH like <3, no corrosion occurs cuz the metal directly reacts with the acid but what about at pH>3?) :rolleyes:
  19. Sirius Black

    probability qs

    help on a similar q 8 members of a tennis club meet to play two simultaneous sets of double tennis on two separate by otherwise identical courts. In how many different ways can 8 members of the club be selected? Is it same to the q if they ask how many different ways to arrange 8 ppl into 4...
  20. Sirius Black

    two confusing dot points

    describe factors that affect an electrolysis reaction -effect of concentration -nature of electrolyte -nature of electrodes This looks quite similar to the prac"plan and perform a first-hand investigation and gather first-hand data to identify the factors that affect the rate of an...