Question

Show that all roots of the equation 4=1 forms a commutative group under the operation
usual multiplication.

Answer 1

Answer:

invertible elements, or units, form an abelian multiplicative group. In particular, the real numbers are an abelian group under addition, and the nonzero real numbers are an abelian group under multiplication. ... The finite simple abelian groups are exactly the cyclic groups of prime order.

Free abelian group