(2x-3)(x²-4xy-y²)+(3-2x)(x²-5xy+2y²)=(2x-3)(x²-4xy-y²)-(2x-3)(x²-5xy+2y²)=(2x-3)(x²-4xy-y²-x²+5xy-2y²)=(2x-3)(xy-3y²)=2x²y-6xy²-3xy+9y²
(2x-3)(x²-4xy-y²)+(3-2x)(x²-5xy+2y²)=(2x-3)(x²-4xy-y²)-(2x-3)(x²-5xy+2y²)=(2x-3)(x²-4xy-y²-x²+5xy-2y²)=(2x-3)(xy-3y²)=2x²y-6xy²-3xy+9y²