4.
如图,六边形ABCDEF中,AB∥DE,BC∥EF,CD∥AF.现有以下结论:①∠A+∠C+∠E=360°;②∠B+∠C+∠D=360°;③AB=DE.其中正确的结论有( )
| A. | ①②③ | B. | ①② | C. | ①③ | D. | ②③ |
2.用“描点法”画二次函数y=ax2+bx+c(a≠0)的图象时,列出了表格:那么该二次函数有最小(填“大”或“小”)值-1.
0 298410 298418 298424 298428 298434 298436 298440 298446 298448 298454 298460 298464 298466 298470 298476 298478 298484 298488 298490 298494 298496 298500 298502 298504 298505 298506 298508 298509 298510 298512 298514 298518 298520 298524 298526 298530 298536 298538 298544 298548 298550 298554 298560 298566 298568 298574 298578 298580 298586 298590 298596 298604 366461
| x | … | 1 | 2 | 3 | 4 | … |
| y=ax2+bx+c | … | 0 | -1 | 0 | 3 | … |