(2x-3y)(3y+2x)-(2x-y)²=(2x)²-(3y)²-(4x²-4xy+y²)
=4x²-9y²-4x²+4xy-y²
=4x²-4x²+4xy-9y²-y²
=4xy-10y²
=y(4x-10y)
=1*(4*1/4-10)
=1-10
=-9