3x²y+{xy-[3x²y-(4xy²+1/2xy)]-(4x²y+3/2xy)}
=3x²y+xy-3x²y+4xy²+1/2xy-4x²y-3/2xy
=xy+1/2xy-3/2xy+4xy²-4x²y
=4xy²-4x²y
=4xy(y-x)
3x²y+{xy-[3x²y-(4xy²+1/2xy)]-(4x²y+3/2xy)}
=3x²y+xy-3x²y+4xy²+1/2xy-4x²y-3/2xy
=xy+1/2xy-3/2xy+4xy²-4x²y
=4xy²-4x²y
=4xy(y-x)