$gt\Leftrightarrow (\sqrt{a}-\sqrt{b}^2+(\sqrt{b}-\sqrt{c})^2+(\sqrt{c}-\sqrt{a})^2=0$$\Rightarrow \sqrt{a}=\sqrt{b}=\sqrt{c}\Rightarrow a=b=c$$\Rightarrow \triangle $ đều
$gt\Leftrightarrow (\sqrt{a}-\sqrt{b}
)^2+(\sqrt{b}-\sqrt{c})^2+(\sqrt{c}-\sqrt{a})^2=0$$\Rightarrow \sqrt{a}=\sqrt{b}=\sqrt{c}\Rightarrow a=b=c$$\Rightarrow \triangle $ đều