Answer
$-6$
Work Step by Step
Our aims is to compute the dot product , for this we will multiply the corresponding components together and then add.
In general, we have the formula as: $ \lt a , b\gt \cdot \lt c, d \gt =ac+bd$
We have: $u=\lt -2, 1 \gt $ and $v = \lt 3, 4 \gt $
Now, $3u= 3 \lt -2, 1 \gt= \lt -6, 3 \gt$
Therefore,
$3u \cdot v = \lt -6, 3 \gt \cdot \lt 3, 4 \gt \\= (-6) (3) +(3)(4) \\= -18+12 \\=-6$
