因为|a-1/2|≥0,（b+1/3）²≥0又|a-1/2|+（b+1/3）²=0所以|a-1/2|=0,（b+1/3）²=0即：a=1/2,b=-1/34a²-2ab-b² =4×(1/2)²-2×(1/2)×(-1/3)-(-1/3)²=1+1/3-1/9=11/9...