\(\overrightarrow{AD}=\overrightarrow{BC}\Rightarrow T=\left|\overrightarrow{AB}+3\overrightarrow{AD}\right|\)
\(T^2=AB^2+9AD^2+6\overrightarrow{AB}.\overrightarrow{AD}\) (để ý rằng AB, AD vuông góc nên \(\overrightarrow{AB}.\overrightarrow{AD}=0\))
\(T^2=AB^2+9AD^2=2^2+9.3^2=85\)
\(\Rightarrow T=\sqrt{85}\)