## Algebra and Trigonometry 10th Edition

$||v||=2\sqrt {53}$
$v$ goes from $(1,5)$ to $(15,9)$ $v=⟨15-1,9-5⟩=⟨14,4⟩$ $||v||=\sqrt {v·v}=\sqrt {⟨14,4⟩·⟨14,4⟩}=\sqrt {14^2+4^2}=\sqrt {196+16}=\sqrt {212}=\sqrt {4·53}=2\sqrt {53}$