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Mathematics 15 Online
OpenStudy (anonymous):

Homework help Anyone?

OpenStudy (anonymous):

OpenStudy (anonymous):

@ganeshie8 kindly

ganeshie8 (ganeshie8):

which q ?

OpenStudy (anonymous):

sorry 1 and 3 sorry

OpenStudy (anonymous):

Available?

ganeshie8 (ganeshie8):

#1 should be easy if you are familiar with powerset

ganeshie8 (ganeshie8):

{a, b, c} lets list all the subsets with 0/1/2/3 elements : 0 : {} 1 : {a}, {b}, {c} 2 : {a, b}, {b, c}, {c, a} 3 : {a, b, c}

ganeshie8 (ganeshie8):

count them for part b

OpenStudy (anonymous):

can u help me with that

OpenStudy (anonymous):

count them for b ? like add all the ones given above ?

OpenStudy (anonymous):

there ?

ganeshie8 (ganeshie8):

powerset of set A is a collection of all the subsets of A. cardinality of a finite set is the number of elements in a set

ganeshie8 (ganeshie8):

how many subsets are there for the set {a, b, c} ?

OpenStudy (anonymous):

three

ganeshie8 (ganeshie8):

what are they ?

OpenStudy (anonymous):

{a,b}, {b,c} and {c,a}

ganeshie8 (ganeshie8):

those are subsets with just two elements

ganeshie8 (ganeshie8):

what about the subsets with 1 element, 3 elements and 0 elements ?

ganeshie8 (ganeshie8):

0 : `{}` 1 : `{a}`, `{b}`, `{c}` 2 : `{a, b}`, `{b, c}`, `{c, a}` 3 : `{a, b, c}`

OpenStudy (anonymous):

ok i get you.

ganeshie8 (ganeshie8):

number of subsets with 0 elements = 1 number of subsets with 1 elements = 3 number of subsets with 2 elements = 3 number of subsets with 3 elements = 1

ganeshie8 (ganeshie8):

total number of subsets = ?

OpenStudy (anonymous):

8

ganeshie8 (ganeshie8):

yes so we say the cardinality of powerset of {a, b, c} is 8

ganeshie8 (ganeshie8):

it refers to the size of a set

ganeshie8 (ganeshie8):

and the powerset of {a, b, c} would be : { {}, {a}, {b}, {c}, {a, b}, {b, c}, {c, a}, {a, b, c} }

OpenStudy (anonymous):

possible subsets for {a,b,c,d} will be 10?

ganeshie8 (ganeshie8):

try again

ganeshie8 (ganeshie8):

list them by size

ganeshie8 (ganeshie8):

subsets with 0 elements : {}

ganeshie8 (ganeshie8):

subsets with 1 elements : {a}, {b}, {c}, {d}

ganeshie8 (ganeshie8):

etc..

OpenStudy (anonymous):

ok just a min

OpenStudy (anonymous):

11?

ganeshie8 (ganeshie8):

list them all

ganeshie8 (ganeshie8):

list all the subsets with 2 elements

OpenStudy (anonymous):

{a,b} {b,c} {c,d} {d,a} {b,d} {a,d}

ganeshie8 (ganeshie8):

Right, next list down all the subsets with 3 elements?

OpenStudy (anonymous):

{a,b,c} {b,c,d} {a,b,d} {a,c,d}

ganeshie8 (ganeshie8):

next list all the subsets with 4 elements

OpenStudy (anonymous):

{a,b,c,d}

ganeshie8 (ganeshie8):

so total how many subsets you got ?

OpenStudy (anonymous):

12

ganeshie8 (ganeshie8):

number of subsets with 0 elements : 1 number of subsets with 1 elements : 4 number of subsets with 2 elements : 6 number of subsets with 3 elements : 4 number of subsets with 4 elements : 1

ganeshie8 (ganeshie8):

add them again

OpenStudy (anonymous):

sorry sorry

OpenStudy (anonymous):

did not count some

OpenStudy (anonymous):

cardinalty is the total number of subsets

ganeshie8 (ganeshie8):

cardinality of a set is the total number of elements in it

ganeshie8 (ganeshie8):

powerset is a collection of all the subsets

OpenStudy (anonymous):

so for {a,b,c,d } cardinality is 4

ganeshie8 (ganeshie8):

Yep!

OpenStudy (anonymous):

Thankya. For section (e) ?

ganeshie8 (ganeshie8):

do you see any pattern ?

OpenStudy (anonymous):

i cant guess.

OpenStudy (anonymous):

Available?

ganeshie8 (ganeshie8):

cardinality of powerset with 3 elements = 8 = 2^3 cardinality of powerset with 4 elements = 16 = 2^4 ... cardinality of powerset with n elements = 2^n ?

ganeshie8 (ganeshie8):

https://proofwiki.org/wiki/Cardinality_of_Power_Set

OpenStudy (anonymous):

Thank you

OpenStudy (anonymous):

Question 3 please.

ganeshie8 (ganeshie8):

hey il need to review my analysis notes a bit to answer that

ganeshie8 (ganeshie8):

maybe close this question and open a new question for #3, il try to answer if nobody does..

OpenStudy (anonymous):

ok. Thank you.

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