6.数列{an}满足a1=1,an+1=an+n+1(n∈N•),则$\frac{1}{{a}_{1}}$+$\frac{1}{{a}_{2}}$+…+$\frac{1}{{a}_{2015}}$等于( )
A. | $\frac{2015}{2016}$ | B. | $\frac{4028}{2015}$ | C. | $\frac{2015}{1008}$ | D. | $\frac{1007}{1008}$ |
19.已知2014${\;}^{{x}^{2}}$•2014-y•20142x=1,则函数y=f(x)的值域是( )
0 249615 249623 249629 249633 249639 249641 249645 249651 249653 249659 249665 249669 249671 249675 249681 249683 249689 249693 249695 249699 249701 249705 249707 249709 249710 249711 249713 249714 249715 249717 249719 249723 249725 249729 249731 249735 249741 249743 249749 249753 249755 249759 249765 249771 249773 249779 249783 249785 249791 249795 249801 249809 266669
A. | R | B. | [-1,+∞) | C. | (-∞,-1] | D. | 无法确定 |