Answer:
1. Not a direct variation
2. Direct variation (constant= -4)
3. Direct variation (constant= -1)
Step-by-step explanation:
A direct variation is a function of the type
y = k*x, where k can be any real number
First case
1. y=4x+9
The term 9 interferes with the expression (it creates an offset for the value)
2. 2y=-8x
It is a direct variation, y = -4x
3. x+y=0
It is a direct variation, y = -x
