=log2[(x+2)^2/x]
=log2[2(x/2+2/x)+4]
x=2时,f(x)取得最小值 f(x)=3
2、因为:a+b+c=3
所以:b^2=(3-a-b)^=(a-3)^2+(b-3)^2-9+2ac
因为:a、b、c呈等比数列
所以:b^2=ac
b^2=9-(a-3)^-(b-3)^2
b∈[-3,3]
3、loga(t+1/2)-(1/2)loga(t)
=loga[(t+1/2)/√t)
=loga√[1+(t+1/4t)]
0loga(t+1/2)
a>1时:(1/2)loga(t)