18.如果单项式-5xa+1y4与2ybx3是同类项,那么a、b的值分别是( )
| A. | a=1,b=4 | B. | a=1,b=3 | C. | a=2,b=4 | D. | a=2,b=3 |
17.在-5,0,$\frac{2}{5}$,2.5这四个数中,绝对值最大的数是( )
0 279567 279575 279581 279585 279591 279593 279597 279603 279605 279611 279617 279621 279623 279627 279633 279635 279641 279645 279647 279651 279653 279657 279659 279661 279662 279663 279665 279666 279667 279669 279671 279675 279677 279681 279683 279687 279693 279695 279701 279705 279707 279711 279717 279723 279725 279731 279735 279737 279743 279747 279753 279761 366461
| A. | -5 | B. | 0 | C. | $\frac{2}{5}$ | D. | 2.5 |