函数y=x²+bx+c与y=x的图像如图所示，有以下结论：

①b²﹣4c＞0；②3b+c+6=0；③当1＜x＜3时，x²+（b﹣1）x+c＜0；

④ $\sqrt{b^2+c^2}=3\sqrt{2}$ ，其中正确的有____

    Do you want to be healthy and thin? All of us will say: of course! But how to be healthy and thin? If you want to lose weight and keep healthy, the first way is to be on a diet. Eating too much is bad for your health and you will easily turn fat! The best way is to eat a little sugar, but more vegetables! The other way is to do more exercise! Sport is good for your health. You should keep running or walking for about twenty minutes every day. This is the most straightforward method. If you keep doing this for a long time, you will be more healthy.

(词汇提示：1) lose weight 减肥  2） be on a diet 按规定进食；节食  3）a little 少量的 
4）method方法  5）the most straightforward method最直接的方法)