For questions 1-3
determine whether the equation represents a direct variation. if it does, find the constant of variation.

1. 2 y = 5x +1
a. not a direct variation
b. direct variation, constant of variation is 5/2
c. direct variation, constant of variation is 2/5
d. direct variation, constant of variation is 1 -2/5

2. -12x = 6y
a. not a direct variation
b. direct variation, constant of variation is 1/2
c. direct variation, constant of variation is 2
d. direct variation, constant of variation is -2

3. 7x -1.4y = 0
a. not a direct variation
b. direct variation, constant variation is 1/2
c. direct variation, constant variation is 2
d. direct variation, constant variation is -2

for questions 4-6
suppose y varies directly with x. write a direct variation equation that relates x and y.

4. y= -10 when x =2
a. y= -5x
b. y= -1/5x
c. y= 5x
d. y= 1/5 x

5. y= 7 1/2 when x=3
a. y= 3/2x
b. y= 2/3x
c. y= 5/2
d. y= 2/5
6. y=10.4 when x=4
a. y= 3.4x
b. y= 3.8x
c. y= 3.2x
d. y= 2.6x

for questions 7 and 8
for the data in the table, tell whether y varies directly with x. if it does, write an equation for the direct variation.

7. (x. y)
(3, 5.4)
(7, 12.6)
(12, 21.6)

a. not a direct variation
b. direct variation, y= 1.8x
c. direct variation, y= 4x
d. direct variation, y= 5/9x

8. (x, y)
(-2,1)
(3,6)
(8,11)

a. not a direction variation
b. direct variation, y=x
c. direct variation, y=2x
d. direct variation, y= -2x