9.下列各式中运算正确的是( )
| A. | 3m-m=2 | B. | a2b-ab2=0 | C. | 2x+3y=5xy | D. | xy-2xy=-xy |
8.若ab2n-1与abn+1是同类项,则n的值是( )
0 279491 279499 279505 279509 279515 279517 279521 279527 279529 279535 279541 279545 279547 279551 279557 279559 279565 279569 279571 279575 279577 279581 279583 279585 279586 279587 279589 279590 279591 279593 279595 279599 279601 279605 279607 279611 279617 279619 279625 279629 279631 279635 279641 279647 279649 279655 279659 279661 279667 279671 279677 279685 366461
| A. | 2 | B. | 1 | C. | -1 | D. | 0 |