A:﹣ 358
B:358
C:﹣70
D:70
若ai,bi∈R+i=1,2,3,...,n ,求证a1b1+···+anbna1b1+···+anbn≥a1+···+an2 .
- The storybook is very interesting.
- I agree with you. I ______ it twice already.