x²-6xy+9xy²-3x/2+9y/2+m/2错了吧应该是x²-6xy+9y²-3x/2+9y/2+m/2=(x-3y)²-(3/2)(x-3y)+m/2=(x-3y)²-(3/2)(x-3y)+9/16-9/16+m/2=(x-3y-3/4)²-9/16+m/2是完全平方式所以-9/16+m/2=0m=9/8
