3.下列变形正确的是( )
| A. | 若-$\frac{1}{2}$x>1,则x>-2 | B. | 若a<b,b>c,则a<c | ||
| C. | 若a>b,则$\frac{a}{b}$>1 | D. | 若x-1>y+2,则x-y>3 |
2.用代数式表示“a的2倍与-1的和是非负数”,正确的是( )
| A. | 2a-1≥0 | B. | 2a+1≥0 | C. | 2a-1<0 | D. | 2a+1<0 |
18.下列各数中,比-1小的是( )
| A. | 0 | B. | 0.1 | C. | 1 | D. | -52 |
17.下列图形既是轴对称图形,又是中心对称图形的是( )
| A. | B. | C. | D. |
16.
如图,△ABC中,AD⊥BC于D,BE⊥AC于E,AD交BE于点F,若BF=AC,则∠ABC等于( )
0 294527 294535 294541 294545 294551 294553 294557 294563 294565 294571 294577 294581 294583 294587 294593 294595 294601 294605 294607 294611 294613 294617 294619 294621 294622 294623 294625 294626 294627 294629 294631 294635 294637 294641 294643 294647 294653 294655 294661 294665 294667 294671 294677 294683 294685 294691 294695 294697 294703 294707 294713 294721 366461
| A. | 45° | B. | 48° | C. | 50° | D. | 60° |