how do you read a graph if it changes?

Question

the equation is y=2/5x+3 and its graphed in the graphs below, but it says which graph shows the result of changing the 3 in the equation to -1? please help!

Answer 1

1 ) The equation is y = (2/5)x + 3.

Compare the equation with slope-intercept form y = mx + b.

slope = 2/5 and y-intercept is 3.

y-intercept is 3, so the line crosses the y-axis at (0, 3)

Using slope find the next point.

Slope = rise/run = 2/5

Start at point (0,3), move 2 unit up and 5 units right, then plot the point (5,5).

Draw a line through these points.

2)  y = (2/5)x + 3

In the above equation 3 is substitute by -1.

The equation is y = (2/5)x - 1.

Compare the equation with slope-intercept form y = mx + b.

slope = 2/5 and y-intercept is -1.

y-intercept is 3, so the line crosses the y-axis at (0, -1)

Using slope find the next point.

Slope = rise/run = 2/5

Start at point (0,-1), move 2 unit up and 5 units right, then plot the point (5,1).

Draw a line through these points.

 

Graph :

So the lines are parallel.