In the equation y = 2x+4 just put the value of x = 0,1,2,3,4.... In order to get the value of y like this

If x = 0 then

y = 2x+4

y = 2(0)+4

y = 0+4

y = 4

(x,y) = (0,4)

if x = 1 then

y = 2x+4

y = 2(1)+4

y = 2+4

y = 6

(x,y) = (1,6)

if x = 2 then

y = 2x+4

y = 2(2)+4

y = 4+4

y = 8

(x,y) = (2,8)

if x = 3 then

y = 2x+4

y = 2(3)+4

y = 6+4

y = 10

(x,y) = (3,10)

if x = 4 then

y = 2x+4

y = 2(4)+4

y = 8+4

y = 12

(x,y) = (4,12)

x | y

0 | 4

1 | 6

2 | 8

3 | 10

4 | 12

.

.

.

and so on

Now you have x and y coordinates, so it is easy to make the graph. The value of x and y shows that the line lies in 1st quadrant only if the value of x is Positive.

If x = 0 then

y = 2x+4

y = 2(0)+4

y = 0+4

y = 4

(x,y) = (0,4)

if x = 1 then

y = 2x+4

y = 2(1)+4

y = 2+4

y = 6

(x,y) = (1,6)

if x = 2 then

y = 2x+4

y = 2(2)+4

y = 4+4

y = 8

(x,y) = (2,8)

if x = 3 then

y = 2x+4

y = 2(3)+4

y = 6+4

y = 10

(x,y) = (3,10)

if x = 4 then

y = 2x+4

y = 2(4)+4

y = 8+4

y = 12

(x,y) = (4,12)

x | y

0 | 4

1 | 6

2 | 8

3 | 10

4 | 12

.

.

.

and so on

Now you have x and y coordinates, so it is easy to make the graph. The value of x and y shows that the line lies in 1st quadrant only if the value of x is Positive.