First of all, there are 1 1 formulas of inequality properties in the book. On page 64 of compulsory five. Mean inequality formula 1, harmonic mean: HN = n/(1/a1/a2+...+1/an) 2, geometric mean: GN = (A 1A2 ... an. 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 a65438. (A 1A2...an) (1/n) (when r=0) (that is, d (0) = (a1a2 ... an) (1/n)) There are: when r notices HN ≤ GN There is a simple conclusion that middle schools often use 2/(1/a+1/b) ≤√ AB ≤ (a+b)/2 ≤√ [(A2+B2)/2].