因为x-y+1的平方根是它本身,所以x-y+1=0,
因为三次根号x-2y与三次根号x+y-3互为相反数,所以x-2y与x+y-3为互为相反数,
x-2y+x+y-3=0,2x-y-3=0,因为x-y+1=0,所以 x=4,y=5