19.下面计算正确的是( )
| A. | $\sqrt{3}$+$\sqrt{5}$=$\sqrt{8}$ | B. | $\sqrt{2}$×$\sqrt{3}$=$\sqrt{6}$ | C. | $\sqrt{(-3)^{2}}$=-3 | D. | $\sqrt{7}$-$\sqrt{5}$=$\sqrt{2}$ |
18.
如图,点A表示的实数是( )
0 279666 279674 279680 279684 279690 279692 279696 279702 279704 279710 279716 279720 279722 279726 279732 279734 279740 279744 279746 279750 279752 279756 279758 279760 279761 279762 279764 279765 279766 279768 279770 279774 279776 279780 279782 279786 279792 279794 279800 279804 279806 279810 279816 279822 279824 279830 279834 279836 279842 279846 279852 279860 366461
| A. | $-\sqrt{5}$ | B. | $\sqrt{5}$ | C. | $-\sqrt{3}$ | D. | $\sqrt{3}$ |