in set theory, a union of a set of sets is a set consisting of all the elements of those sets and no other elements.

for two given sets a and b, the set composed of all the elements belonging to set a or set b (the set composed of all the elements of the two sets combined with the sum of all the elements of the two sets) is called the union, denoted as a∪ b, pronounced "a and b". expressed symbolically, that is: a∪b={xix∈a or x∈b}

formula for the sum of cubes of continuous natural numbers: s(n)=1³ + ... + n³ = [n/2(1 + n)]²