Factorize $8x^3 + 36x^2 y + 54xy^2 + 27y^3$:

The expression matches the perfect-cube pattern $(2x)^3 + 3(2x)^2(3y) + 3(2x)(3y)^2 + (3y)^3 = (2x+3y)^3$. Each coefficient () fits exactly.