Concept: 1, harmonic mean: HN = n/(1/a1/a2+...+1/an) 2, geometric mean: GN = (A 1A2 ... an. N 4, square average: qn = √ [(a12+A22+...+an2)/n] These four average values satisfy Hn≤Gn≤An≤Qn a 1, a2, ..., an∈R+ if and only if A. That is, d (-1) ≤ d (0) ≤ d (1) ≤ d (2) is simplified from the above, and there is a simple conclusion: 2/(1/a+1/b) ≤√ ab ≤ (a)

I must have learned. .

Since you don't study hard at ordinary times, you can certainly simplify the exam, so don't worry. .