20.已知f(x)=$\frac{{2}^{x}-1}{{2}^{x}+1}$,则满足f(a)-f(-a)<1的a的取值范围是( )
| A. | (-∞,3) | B. | (-∞,log23) | C. | (3,+∞) | D. | (log23,+∞) |
19.若实数x,y满足$\left\{\begin{array}{l}{x≥3}\\{y≤3}\\{{x}^{2}+{y}^{2}=25}\end{array}\right.$,则2x+2y的最大值为( )
| A. | 10$\sqrt{2}$ | B. | 14 | C. | 5$\sqrt{6}$ | D. | 12 |
17.直线AB的斜率为2,其中点A(1,-1),点B在直线y=x+1上,则点B的坐标是( )
0 227425 227433 227439 227443 227449 227451 227455 227461 227463 227469 227475 227479 227481 227485 227491 227493 227499 227503 227505 227509 227511 227515 227517 227519 227520 227521 227523 227524 227525 227527 227529 227533 227535 227539 227541 227545 227551 227553 227559 227563 227565 227569 227575 227581 227583 227589 227593 227595 227601 227605 227611 227619 266669
| A. | (4,5) | B. | (5.7) | C. | (2,1) | D. | (2,3) |