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

Firstly, expand out the (2x+3y)^2 as (2x+3y)(2x+3y).Multiplying each term in the first bracket with each term from the second bracket gives 4x^2+6xy+6xy+9y^2 which simplifies to 4x^2+12xy+9y^2 by adding the two 6xy's together.Now, we need to expand out (x-4)(4x^2+12xy+9y^2), this is done by the same method as above by multiplying out each term in each bracket.This gives 4x^3+12x^2y+9xy^2-16x^2-48xy-36y^2.The final step is to check if there are any common terms which can be simplified down. In this case, it can't be simplified any further.