设点A(1,0)在x轴上，点B(0,3)在y轴上，P是直线x+y=4上的动点，则PA+PB的最小值为    4   .

短文改错

As a middle school student of Senior Three, I do sports one and two hours a day, such as doing morning exercises, playing basketball and long-distance running. I think it is real helpful to me. Take exercise makes me even more healthy so that I won’t be ill very often. What’s more, I also get myself relaxing in different kinds of sports. Only in this way I do a better job in my study in high spirit. By doing physics exercise, I’m becoming stronger and confident than ever. I do not think that this is necessary for everyone to spend a little time on sports every day because people’s health is the most important one in modern life.