One Response to “Help needed…”

1. admin says:

   March 10 at 4:00 am

   In article <89odhi$2m9…@quince.news.easynet.net>, "John"
   

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   <j…@JapanGlobe.net> wrote:
   >I cannot work out answers of the following test:
   

   >Assume A={2,4,5,6} , B={2,6,4} and C={1,4,6}
   >describe the following sets explicitly, listing their members inside curly
   >brackets.

   >I attempted replying on the right…
   >u is for union, P for Power and n Intersection

   >1- {Ø,{Ø,Ø},{Ø},{{Ø}}}    = {Ø,{Ø}}
   >2- Ø u {Ø}                            = {Ø,{Ø}}
   >3- (A u C) – B                        = {2,5}
   >4- P Ø                                    = Ø
   >5- P{Ø}                                 = {Ø,{Ø}}
   >6- P{3,{3}}                            ?
   >7- A n P A                             = Ø
   >8- {3,{3}} n P{3,{3}}           = {3,{3}}
   >9- Ø x Ø                                = {<Ø,Ø>}
   >10- {Ø} x {Ø}                       ={<{Ø},{Ø}>}
   >11- {Ø}x Ø                            ={<{Ø},Ø>}

   >Thanks for correcting me. All explanations are wellcome.
   >Cheers.
   >John

    I am assuming that 0 represents the empty set.
   1- you left something out in your answer.
   2- you put something extra in your answer
   3- you put something in that shouldn’t be and left out something that
   should be in.
   4- you never have P S = S for any set S
   5-
   6- P S always contains as elements 0 and S and any proper subsets of S
   7-
   8- {3,{3}}is not an element of {3,{3}}, so cannot be in {3,{3}} n S
   9- 0 x S = S x 0 = 0 for any S, it is still empty.
   10- {< 0,0 >},since 0 is an element of each, but {0} is not
   11- See 9.

   –
   Virgil
   vm…@frii.com