15.用科学记数法表示的数6.18×10-3,其原数为( )
| A. | 0.618 | B. | 0..618 | C. | 0.00618 | D. | 0.000618 |
14.若(x+3)(x+m)=x2-kx-15,则k+m的值为( )
| A. | -3 | B. | 5 | C. | -2 | D. | 2 |
13.下列各式中,计算结果为m2-4n2的是( )
| A. | (-m-2n) 2n | B. | (m-2n)(2n-m) | C. | (m-2n)(-m-2n) | D. | (2n-m)(-m-2n) |
11.将0.000000424用科学记数法表示为( )
0 283924 283932 283938 283942 283948 283950 283954 283960 283962 283968 283974 283978 283980 283984 283990 283992 283998 284002 284004 284008 284010 284014 284016 284018 284019 284020 284022 284023 284024 284026 284028 284032 284034 284038 284040 284044 284050 284052 284058 284062 284064 284068 284074 284080 284082 284088 284092 284094 284100 284104 284110 284118 366461
| A. | 42.4×10-6 | B. | 4.24×10-7 | C. | 0.424×10-6 | D. | 42.4×10-8 |