perfect square of a sum - 1. binomische Formel
$${ (a + b)^2 = (a + b) \cdot (a + b) = a^2 + 2 \cdot a \cdot b + b^2}$$
perfect square of a difference - 2. binomische Formel
$${ (a - b)^2 = (a - b) \cdot (a - b) = a^2 - 2 \cdot a \cdot b + b^2}$$
alternative
difference of squares - 3. binomische Formel
$${ (a - b) \cdot (a + b) = a^2 - b^2}$$
