The norm of a vector [tex]\vec x[/tex] is equal to the square root of the inner product of [tex]\vec x[/tex] with itself.
a. [tex]\|(-1,2)\|=\sqrt{\langle(-1,2),(-1,2)\rangle}=\sqrt{4(-1)^2+9(2)^2}=\sqrt{40}=2\sqrt{10}[/tex]
b. [tex]\|(3,2)\|=\sqrt{\langle(3,2),(3,2)\rangle}=\sqrt{4(3)^2+9(2)^2}=\sqrt{72}=6\sqrt2[/tex]
