三个数1/a,1,1/c成等差数列,1-1/a=1/c-12=1/a+1/ca+c=2aca^2+2ac+c^2=4a^2c^2a^2+c^2=4a^2c^2-2ac三个数a^2,1,c^2成等比数列,a^2/1=1/c^2a^2c^2=1=(ac)^2ac=1a^2+c^2=4a^2c^2-2ac=4-2=2(a+c)/(a^2+c^2)=2/2=1...