Expansions  of Algebraic Expressions The formula: a(b+c) = ab + ac Algebraic Expansion. (a+b)(c+d)=ac+ad+bc+bd and  (a+b)(a-b)= a ² – b² difference of square (a+b)² = a² + 2ab + b² perfect square (a-b) ²=a²-2ab+b² Expansion