help with algebra! 10 points!?

Question

describe the set {1,5,7,8} using union and intersection

Answer 1

Using union and intersection of what other sets? Are you supposed to make them up?

{1,5,7,8} = {1,5} U {7,8}
{1,5,7,8} = {1,5,7,8,9} ∩ {1,5,7,8,10}

Answer 2

To have union or intersection, you need at least two sets.

For example, {1,5,7,8} is the union of the sets {1,7} and {5,8}.

And {1,5,7,8} is the intersection of the two sets {1,2,3,4,5,6,7,8,9,10} and {-8,-7,-5,-1,1,5,7,8,11,15,17,18}

For union, collect the members of all the sets together.

For intersection, work out what members all the sets have in common.

Answer 3

if you will graph {1,5,7,8} the line will infinitely going up on the x-axis