a大于0,b大于0证明1.a+1/a大于等于22.(a+b)*(1/a+1/b)大于等于4
(1/a+1/b)分之2小于等于跟号ab小于等于a+b/2小于等于跟号a^2+b^2/2
a大于0b大于0.(1/a+1/b)分之2小于等于跟号ab小于等于a+b/2小于等于跟号a^2+b^2/2这个怎么证明?