(2x-3)²-(x+y)(x-y)-y²=4x²-12x+9-(x²-y²)-y²=4x²-12x+9-x²+y²-y²=3x²-12x+9=3(x²-4x)+9根据己知条件得：x²-4x=1，代入得： 原式=3+9=12
