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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