Which equation represents the relationship shown in the graph? a. y=-2x b. y=2x c. y=-1/2x d. y=1/2x

Consider the slope-intercept form y =mx + b, where m is the slope and be is the y-intercept. 
What is the slope (m) of the graph? The points move up 4 and over 2, so the slope equals 4 ÷ 2 = 2. Option B is the only graph with a slope of 2, so we already know that the answer is B) y=2x.

To confirm, check the y-intercept. You can see that the graph will pass through the point (0,0), which means b=0.