Answer
$20$
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$
Therefore,
$ \lt 4, 0 \gt \cdot \lt 5, -9 \gt = (4)(5)+(0)(-9)=20-0=20$
