For the given vectors
and 
The dot product of vectors a and b is defined as = 
So, 

= -16+12
= -4
You can square the whole problem to cancel out the square root. Might make things easier.
Answer:
Step-by-step explanation:
perp. -4/3
y + 2 = -4/3(x - 3)
y + 2 = -4/3x + 4
y = -4/3x + 2