For ten points, identify this general property which is held by a member x of a group if xx = x.
The number of elements in the free monoid described by this term is givenidentify this set of numbers of the form a + bı where ı = Answer: complex numbers n  n  k    2iby k (k − i + 1) . Numbers are said to be this if they are expressible k=0 i=1 n  n−kintheform k k ;thisisbecausethesumfromk=0tonofsuchnumbersgives the number of functions with this property on a set with n elements. Functions having this property include functions mapping sets to their closure and vector space projections.   Absorbing elements have this property for the binary operations under which they absorb; and identity elements always have this property. For ten points, identify this general property which is held by a member x of a group if xx = x.
The number of elements in the free monoid described by this term is givenidentify this set of numbers of the form a + bı
idempotence [accept word forms]