11.用总长为60cm的篱笆围成矩形场地.
(Ⅰ)根据题意,填写下表:
(Ⅱ)设矩形一边长为lm,矩形面积为Sm2,当l是多少时,矩形场地的面积S最大?并求出矩形场地的最大面积;
(Ⅱ)当矩形的长为18m,宽为12m时,矩形场地的面积为216m2.
(Ⅰ)根据题意,填写下表:
| 矩形一边长/m | 5 | 10 | 15 | 20 |
| 矩形面积/m2 | 125 | 200 | 225 | 200 |
(Ⅱ)当矩形的长为18m,宽为12m时,矩形场地的面积为216m2.
4.$\sqrt{(-2)^{2}}$的值等于( )
| A. | -2 | B. | 2或-2 | C. | 4 | D. | 2 |
2.如果$\sqrt{{a}^{2}}$-a=b成立,且b>0,则a取值范围是( )
0 284529 284537 284543 284547 284553 284555 284559 284565 284567 284573 284579 284583 284585 284589 284595 284597 284603 284607 284609 284613 284615 284619 284621 284623 284624 284625 284627 284628 284629 284631 284633 284637 284639 284643 284645 284649 284655 284657 284663 284667 284669 284673 284679 284685 284687 284693 284697 284699 284705 284709 284715 284723 366461
| A. | a<0 | B. | a>0 | C. | a≥0 | D. | 无法确定 |