16.2014年杭州市普高招生报考人数共约49500人,将49500用科学记数法表示为( )
| A. | 495×102 | B. | 49.5×103 | C. | 4.95×104 | D. | 0.495×105 |
15.已知二次函数y=ax2+bx+c,如表是x,y的几组对应值.
则由表中数据知,该函数有最大(填“大”或“小”)值,是4;当x=5时,y=-4.
| x | … | 1 | 2 | 3 | 4 | … |
| y | … | -4 | 2 | 4 | 2 | … |
14.下面四个二次函数解析式中,开口方向不同的那个是( )
| A. | y=2x2-3x+1 | B. | y=(x-5)(x-6) | C. | $y=\frac{1}{2}{({x+1})^2}-3$ | D. | y=x-x2-4 |
12.下列各式是完全平方式的是( )
0 294481 294489 294495 294499 294505 294507 294511 294517 294519 294525 294531 294535 294537 294541 294547 294549 294555 294559 294561 294565 294567 294571 294573 294575 294576 294577 294579 294580 294581 294583 294585 294589 294591 294595 294597 294601 294607 294609 294615 294619 294621 294625 294631 294637 294639 294645 294649 294651 294657 294661 294667 294675 366461
| A. | x2+2xy+4y2 | B. | 25m2+10mn+n2 | C. | a2+ab+b2 | D. | x2-2xy-$\frac{1}{4}$y2 |