Expand and simplify (x − 4)(2x + 3y)^2

Rewrite (x − 4)(2x + 3y)² as (x - 4)(2x + 3y)(2x + 3y)
Multiply out the first two brackets to give -(2x² + 3xy - 8x² - 12y)(2x + 3y)
Multiply out the remaining brackets4x³ + 6x²y - 16x² - 24xy + 24xy + 6x²y + 9xy² - 24xy - 36y²
Simply what's left...4x² + 12x²y + 9xy² – 16x² – 48xy – 36y²
Therefore...(x − 4)(2x + 3y)² = 4x² + 12x²y + 9xy² – 16x² – 48xy – 36y²