Reduce

Reduce[expr, vars] reduces the statement expr by solving equations or inequalities for vars.

Reduce[expr, vars, dom] does the reduction over the specified domain.

Examples

Solve an equation:

Reduce[x^2 - 4 == 0, x]
(* x == -2 || x == 2 *)

With domain:

Reduce[x^2 == 2, x, Reals]
(* x == -Sqrt[2] || x == Sqrt[2] *)

Please visit the official Wolfram Language Reference for more details.