10.某型号的手机连续两次降价,每个售价由原来的1225元降到了625元,设平均每次降价的百分率为x,列出方程正确的是( )
| A. | 625(1+x)2=1225 | B. | 1225(1+x)2=625 | C. | 625(1-x)2=1225 | D. | 1225(1-x)2=625 |
9.用配方法解下列方程,其中应在左右两边同时加上4的是( )
0 288722 288730 288736 288740 288746 288748 288752 288758 288760 288766 288772 288776 288778 288782 288788 288790 288796 288800 288802 288806 288808 288812 288814 288816 288817 288818 288820 288821 288822 288824 288826 288830 288832 288836 288838 288842 288848 288850 288856 288860 288862 288866 288872 288878 288880 288886 288890 288892 288898 288902 288908 288916 366461
| A. | x2-2x=5 | B. | x2-8x=4 | C. | x2-4x-3=0 | D. | x2+2x=5 |