Даны векторы 𝑎 → ( 2 ; 0 ) ${\displaystyle \stackrel{\to }{a}\left(2;0\right)}$ и 𝑏 → ( 1 ; 4 ) . ${\displaystyle \stackrel{\to }{b}\left(1;4\right).}$ Найдите длину вектора 𝑎 → + 3 𝑏 → . ${\displaystyle \stackrel{\to }{a}+3\stackrel{\to }{b}.}$