20.若直线x=-1的倾斜角为α,则α=( )
| A. | 0° | B. | 45° | C. | 90° | D. | 不存在 |
14.已知x,y的取值如下表所示:
如果y与x呈线性相关,且线性回归方程为:$\widehat{y}$=$\widehat{b}$x+$\frac{7}{2}$,则$\widehat{b}$=( )
0 234465 234473 234479 234483 234489 234491 234495 234501 234503 234509 234515 234519 234521 234525 234531 234533 234539 234543 234545 234549 234551 234555 234557 234559 234560 234561 234563 234564 234565 234567 234569 234573 234575 234579 234581 234585 234591 234593 234599 234603 234605 234609 234615 234621 234623 234629 234633 234635 234641 234645 234651 234659 266669
| x | 2 | 3 | 4 |
| y | 5 | 4 | 6 |
| A. | -$\frac{1}{10}$ | B. | -$\frac{1}{2}$ | C. | $\frac{1}{10}$ | D. | $\frac{1}{2}$ |