19.函数y=$\sqrt{x+1}$中自变量x的取值范围是( )
| A. | x>0 | B. | x≥1 | C. | x>-1 | D. | x≥-1 |
15.如果(4a2-3ab2)÷M=-4a+3b2,那么单项式M等于( )
| A. | ab | B. | -ab | C. | -a | D. | -b |
14.下列计算正确的是( )
0 284207 284215 284221 284225 284231 284233 284237 284243 284245 284251 284257 284261 284263 284267 284273 284275 284281 284285 284287 284291 284293 284297 284299 284301 284302 284303 284305 284306 284307 284309 284311 284315 284317 284321 284323 284327 284333 284335 284341 284345 284347 284351 284357 284363 284365 284371 284375 284377 284383 284387 284393 284401 366461
| A. | x6÷x2=x3 | B. | (-x)2•(-x)3=-x5 | C. | (x3)2=x5 | D. | (-2x3y2)2=4x8y4 |