Thread: Sets

Consider the sets of values.

A = {x: - infinity < x < 3}

B = {x:3<x< infinity}

C = {x:x=-3,3}

Find = ( A intersect b ) union C.


Would this be somthing like A = numbers between -3 and negative infinity

b = numbers between 3 and positive infinity

and c = numbers between -3 and 3?


So a intersect b is any number between -3 and 3 and c union ( a intersect b ) is again between -3 and 3?

Originally Posted by el123

Consider the sets of values.

A = {x: - infinity < x < 3}

B = {x:3<x< infinity}

C = {x:x=-3,3}

Find = ( A intersect b ) union C.


Would this be somthing like A = numbers between -3 and negative infinity

b = numbers between 3 and positive infinity

and c = numbers between -3 and 3?


So a intersect b is any number between -3 and 3 and c union ( a intersect b ) is again between -3 and 3?

... they have no elements in common



as you have it written, C is a set with only two elements, 3 and -3.

Thanks skeeter!

Originally Posted by el123

Consider the sets of values.

A = {x: - infinity < x < 3}

B = {x:3<x< infinity}

C = {x:x=-3,3}

Find = ( A intersect b ) union C.


Would this be somthing like A = numbers between -3 and negative infinity

b = numbers between 3 and positive infinity

and c = numbers between -3 and 3?


So a intersect b is any number between -3 and 3 and c union ( a intersect b ) is again between -3 and 3?

Sorry this is supposed to be
a = {negative infinity < x < 3}

b = {-3 < x < infinity.}

c ={ x = -3 , 3}




So as i see it , a intersect b = {-3<x<3}

a intersect b includes all numbers between -3 and 3 but not -3 and 3 themselves.

And since c includes only the values -3 and 3 , the union on (a intersect b) union c = nothing.???


Is this correct?

Originally Posted by el123

Sorry this is supposed to be
a = {negative infinity < x < 3}

b = {-3 < x < infinity.}

c ={ x = -3 , 3}




So as i see it , a intersect b = {-3<x<3}

a intersect b includes all numbers between -3 and 3 but not -3 and 3 themselves.

And since c includes only the values -3 and 3 , the union on (a intersect b) union c = nothing.???


Is this correct?

Considering your revisions, then, no, you are not correct. It is true that

,

but now, since

we have

ok i get it.

So im right with the other values but since c contains -3, 3 and it is now a union of the values in a and b then all the values together are the values in (a intersect b) union c.


Did i just make sense?

Originally Posted by el123

ok i get it.

So im right with the other values but since c contains -3, 3 and it is now a union of the values in a and b then all the values together are the values in (a intersect b) union c.


Did i just make sense?

I think so...

Here's a tip: Think of intersection as "and" and union as "or." So for we want all values that are in both and in . is then all values that are in the first set or in .