# What is the dot product of <5,4,-4> and <-4,1,5 >?

$a \cdot b = 4$
$a = < 5 , 4 , - 4 > \text{ } b = < - 4 , 1 , 5 >$
$a \cdot b = 5 \cdot \left(- 4\right) + 4 \cdot 1 + \left(- 4\right) \cdot 5$
$a \cdot b = - 20 + 4 - 20$
$a \cdot b = 4$