3.下列图形中,既是轴对称图形又是中心对称图形的是( )
| A. | B. | C. | D. |
20.若x-2y的值是3,则1-2x+4y的值是( )
| A. | 7 | B. | 5 | C. | 1 | D. | -5 |
19.下列方程的变形中,正确的是( )
| A. | 若x-4=9,则x=8-4 | B. | 若2(2x+3)=2,则4x+6=2 | ||
| C. | 若-$\frac{1}{2}$x=4,则x=-2 | D. | 若$\frac{1}{3}$-$\frac{x-1}{2}$=1,则去分母得2-3(x-1)=1 |
18.下列式子合并同类项正确的是( )
| A. | 3x+5y=8xy | B. | 15ab-15ba=0 | C. | 3y2-y2=3 | D. | 7x3-6x2=x |
16.据有关资料显示,至2016年,徐州市常住人口约为862.83万人,将862.83万用科学记数法可表示为( )
| A. | 8.6283×104 | B. | 86.283×105 | C. | 8.6283×106 | D. | 8.6283×107 |
15.-$\frac{1}{3}$的绝对值是( )
0 297297 297305 297311 297315 297321 297323 297327 297333 297335 297341 297347 297351 297353 297357 297363 297365 297371 297375 297377 297381 297383 297387 297389 297391 297392 297393 297395 297396 297397 297399 297401 297405 297407 297411 297413 297417 297423 297425 297431 297435 297437 297441 297447 297453 297455 297461 297465 297467 297473 297477 297483 297491 366461
| A. | $\frac{1}{3}$ | B. | -$\frac{1}{3}$ | C. | 3 | D. | -3 |