Simplifying
y(2x + 3y)(2x + 3y)
Multiply (2x + 3y) * (2x + 3y)
y(2x * (2x + 3y) + 3y * (2x + 3y))
y((2x * 2x + 3y * 2x) + 3y * (2x + 3y))
Reorder the terms:
y((6xy + 4x2) + 3y * (2x + 3y))
y((6xy + 4x2) + 3y * (2x + 3y))
y(6xy + 4x2 + (2x * 3y + 3y * 3y))
y(6xy + 4x2 + (6xy + 9y2))
Reorder the terms:
y(6xy + 6xy + 4x2 + 9y2)
Combine like terms: 6xy + 6xy = 12xy
y(12xy + 4x2 + 9y2)
(12xy * y + 4x2 * y + 9y2 * y)
(12xy2 + 4x2y + 9y3)