8.下列函数中,是偶函数的是( )
| A. | f(x)=x | B. | f(x)=|x| | C. | f(x)=x3 | D. | f(x)=$\frac{1}{x}$ |
7.函数f(x)=x2+2x+2的最小值是( )
| A. | -1 | B. | 0 | C. | 1 | D. | 2 |
2.曲线C:$\frac{x^2}{4-k}+\frac{y^2}{k-1}$=1表示双曲线,则k的取值范围为( )
0 224337 224345 224351 224355 224361 224363 224367 224373 224375 224381 224387 224391 224393 224397 224403 224405 224411 224415 224417 224421 224423 224427 224429 224431 224432 224433 224435 224436 224437 224439 224441 224445 224447 224451 224453 224457 224463 224465 224471 224475 224477 224481 224487 224493 224495 224501 224505 224507 224513 224517 224523 224531 266669
| A. | 1<k<4 | B. | k>4 | C. | k<0 | D. | k<1或k>4 |