ExpandDenominator

ExpandDenominator[expr] expands out products and powers that appear as denominators in expr.

Examples

Expand a denominator:

ExpandDenominator[1/(a + b)^2]
(* 1/(a^2 + 2 a b + b^2) *)

Only the denominator is expanded:

ExpandDenominator[(x + y)^2/(a + b)^2]
(* (x + y)^2/(a^2 + 2 a b + b^2) *)

Please visit the official Wolfram Language Reference for more details.