若数列{an}满足an+1=且a1=0,则a7= .
若f(10x)=x,则f(5)= .
(x,y)在映射f下的象是(xy,x+y),则点(2,3)在f下的象是 .
若2x-3-x≥2-y-3y,则
A.x-y≥0 B.x-y≤0 C.x+y≥0 D.x+y≤0
若数列{an}是公差为的等差数列,它的前100项和为145,则a1+a3+a5+…+a99的值是
A.60 B.72.5 C.85 D.120
若{an}是等比数列,且an>0,a2a4+2a3a5+a4a6=25,则a3+a5的值为
A.5 B.10 C.15 D.20