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若函数f(x)定义域为R,满足对任意x 1 ,x 2 ∈R,有f(x 1 +x 2 )≤f(x 1 )+f(x 2 ),则称f(x)为“V形函数”;若函数g(x)定义域为R,g(x)恒大于0,且对任意x 1 ,x 2 ∈R,有lgg(x 1 +x 2 )≤lgg(x 1 )+lgg(x 2 ),则称g(x)为“对数V形函数”. (1)当f(x)=x 2 时,判断f(x)是否为V形函数,并说明理由; (2)当g(x)=x 2 +2时,证明:g(x)是对数V形函数; (3)若f(x)是V形函数,且满足对任意x∈R,有f(x)≥2,问f(x)是否为对数V形函数?证明你的结论.