7.设x3=8,则f(x)=(x-1)(x+1)(x2+x+1)的值是( )
| A. | 7 | B. | 15 | C. | 35 | D. | 21 |
6.己知A、F分别为双曲线C的左顶点和右焦点,点D在C上,△AFD是等腰直角三角形,且∠AFD=90°,则C的离心率为( )
| A. | $\sqrt{2}$ | B. | $\sqrt{3}$ | C. | 2 | D. | $\sqrt{2}$+1 |
4.
如图,已知直三棱柱ABC-A1B1C1的侧棱长是2,底面△ABC是等腰直角三角形,且∠ACB=90°,AC=2,E是AB的中点,D是AA1的中点,则三棱锥D-B1C1E的体积是( )
| A. | 1 | B. | $\frac{1}{3}$ | C. | $\frac{\sqrt{2}}{3}$ | D. | $\frac{2}{3}$ |
3.已知i是虚数单位,若在z(1+2i)=i,则z的虚部为( )
0 224331 224339 224345 224349 224355 224357 224361 224367 224369 224375 224381 224385 224387 224391 224397 224399 224405 224409 224411 224415 224417 224421 224423 224425 224426 224427 224429 224430 224431 224433 224435 224439 224441 224445 224447 224451 224457 224459 224465 224469 224471 224475 224481 224487 224489 224495 224499 224501 224507 224511 224517 224525 266669
| A. | $\frac{1}{5}$ | B. | -$\frac{1}{5}$ | C. | $\frac{i}{5}$ | D. | -$\frac{i}{5}$ |