2.已知曲线y=$\frac{1}{{e}^{x}+1}$,则曲线的切线斜率取得最小值时的直线方程为( )
A. | x+4y-2=0 | B. | x-4y+2=0 | C. | 4x+2y-1=0 | D. | 4x-2y-1=0 |
1.若等差数列{an}满足a12+a32=2,则$\frac{{{a}_{3}}^{2}+{{a}_{4}}^{2}}{{{a}_{4}}^{2}+{{a}_{5}}^{2}}$的取值范围是( )
0 249487 249495 249501 249505 249511 249513 249517 249523 249525 249531 249537 249541 249543 249547 249553 249555 249561 249565 249567 249571 249573 249577 249579 249581 249582 249583 249585 249586 249587 249589 249591 249595 249597 249601 249603 249607 249613 249615 249621 249625 249627 249631 249637 249643 249645 249651 249655 249657 249663 249667 249673 249681 266669
A. | [1,3] | B. | [$\sqrt{5}$-1,$\sqrt{5}$十1] | C. | [3-2$\sqrt{2}$,3+2$\sqrt{2}$] | D. | [4-2$\sqrt{3}$,4+2$\sqrt{3}$]. |