Dot Product

Thanks for the help guys!! i see where i went wrong now. 

Remember that if we have u = < u₁ , u₂ > and v = < v₁ , v₂ > .... the dot product is just a scalar given by:

(u₁* v₁) +  (u₂* v₂)  =  dot product

Try it again.......there shouldn't be any decimals in this answer....repost if you still have trouble.......

$$\\\boxed{\vec{v}*\vec{u} = \begin{pmatrix} \textcolor[rgb]{1,0,0}{v_1}\\ \textcolor[rgb]{0,0,1}{v_2} \end{pmatrix} * \begin{pmatrix} \textcolor[rgb]{1,0,0}{u_1}\\ \textcolor[rgb]{0,0,1}{u_2} \end{pmatrix} = \begin{pmatrix} \textcolor[rgb]{1,0,0}{v_1}*\textcolor[rgb]{1,0,0}{u_1} + \textcolor[rgb]{0,0,1}{v_2}*\textcolor[rgb]{0,0,1}{u_2} \end{pmatrix}}\\
\boxed{\vec{v}*\vec{u} = \begin{pmatrix} \textcolor[rgb]{1,0,0}{3}\\ \textcolor[rgb]{0,0,1}{8} \end{pmatrix} * \begin{pmatrix} \textcolor[rgb]{1,0,0}{2}\\ \textcolor[rgb]{0,0,1}{-6} \end{pmatrix} = \begin{pmatrix} \textcolor[rgb]{1,0,0}{3}*\textcolor[rgb]{1,0,0}{2} + \textcolor[rgb]{0,0,1}{8}*\textcolor[rgb]{0,0,1}{(-6)} \end{pmatrix}=\textcolor[rgb]{1,0,0}{6}\textcolor[rgb]{0,0,1}{-48}=-42}$$

This is wrong: $$\sqrt{(3*2)^2+(8*(-6))^2} = 48.374 \;?!$$