2x²+6x+y²=2xy-9x²-2xy+y²+x²+6x+9=0(x-y)²+(x+3)²=0因：(x-y)²≥0,(x+3)²≥0所以有：(x-y)²=0,(x+3)²=0解得：x=y=-3所以可得：xy²=-3X(-3)²=-27...