10.设一元二次方程2x2-2x-4=0的两个实根为x1和x2,则下列结论正确的是( )
| A. | x1+x2=2 | B. | x1+x2=-4 | C. | x1•x2=-2 | D. | x1•x2=4 |
9.下列计算正确的是( )
0 309914 309922 309928 309932 309938 309940 309944 309950 309952 309958 309964 309968 309970 309974 309980 309982 309988 309992 309994 309998 310000 310004 310006 310008 310009 310010 310012 310013 310014 310016 310018 310022 310024 310028 310030 310034 310040 310042 310048 310052 310054 310058 310064 310070 310072 310078 310082 310084 310090 310094 310100 310108 366461
| A. | $\sqrt{48}$×$\sqrt{3}$=12 | B. | 2$\sqrt{3}$+3$\sqrt{2}$=5$\sqrt{5}$ | C. | $\sqrt{(π-3.14)^{2}}$=3.14-π | D. | $\sqrt{6}$÷($\sqrt{3}$-$\sqrt{2}$)=$\sqrt{2}$-$\sqrt{3}$ |