15.下列计算不正确的是( )
| A. | m4•m5=m9 | B. | 5x-7x=-2x | ||
| C. | (-x)5÷(-x)2=-x3 | D. | $\frac{{a}^{2}+4a+4}{-{a}^{2}+4}$=$\frac{a+2}{a-2}$ |
14.2017年消费者的旅游消费不断升级.根据国家旅游局数据中心综合测算,2017年春节期间,全国共接待游客3.44亿人次,实现旅游总收入4233亿元.将4233亿用科学记数法表示( )
| A. | 4.233×109 | B. | 4.233×1010 | C. | 4.233×1011 | D. | 4.233×1012 |
10.若二次函数y=(m-1)x2+2x+1的图象与x轴有两个不同的交点,则m的取值范围是( )
| A. | m≤2 | B. | m<2 | C. | m≤2且m≠1 | D. | m<2且m≠1 |
9.下列运算正确的是( )
| A. | a2•a5=a10 | B. | (a2)5=a10 | C. | a2+a5=a7 | D. | (a-b)2=a2-b2 |
8.在-2、1、-$\sqrt{5}$、0这四个数中,最小的实数是( )
0 294201 294209 294215 294219 294225 294227 294231 294237 294239 294245 294251 294255 294257 294261 294267 294269 294275 294279 294281 294285 294287 294291 294293 294295 294296 294297 294299 294300 294301 294303 294305 294309 294311 294315 294317 294321 294327 294329 294335 294339 294341 294345 294351 294357 294359 294365 294369 294371 294377 294381 294387 294395 366461
| A. | -2 | B. | 1 | C. | -$\sqrt{5}$ | D. | 0 |