16.如图,AC⊥l于点C,BD⊥l于点D,且AC=5,BD=11,CD=12.
(1)在直线l上找一点M,使MA=MB,求点M到点D的距离.
(2)在直线l上找一点N,使NA+NB最小,求出这个最小值.
(1)在直线l上找一点M,使MA=MB,求点M到点D的距离.
(2)在直线l上找一点N,使NA+NB最小,求出这个最小值.
15.计算(-12)-(-3)+(-10)-(-9)-$\frac{1}{3}$的结果是( )
| A. | $-\frac{25}{3}$ | B. | $-\frac{43}{3}$ | C. | $-\frac{49}{3}$ | D. | $-\frac{31}{3}$ |
14.下列四个式子中,属于代数式的是( )
| A. | x+y=y+x | B. | -a | C. | S=$\frac{1}{2}ah$ | D. | 3x-1>0 |
8.已知xy>0,化简二次根式x$\sqrt{\frac{-y}{{x}^{2}}}$的正确结果为( )
0 286685 286693 286699 286703 286709 286711 286715 286721 286723 286729 286735 286739 286741 286745 286751 286753 286759 286763 286765 286769 286771 286775 286777 286779 286780 286781 286783 286784 286785 286787 286789 286793 286795 286799 286801 286805 286811 286813 286819 286823 286825 286829 286835 286841 286843 286849 286853 286855 286861 286865 286871 286879 366461
| A. | $\sqrt{y}$ | B. | $\sqrt{-y}$ | C. | -$\sqrt{y}$ | D. | -$\sqrt{-y}$ |