Explain how to determine if a proportional relationship exists between two variables in a graph

Here are some steps to determine if a proportional relationship exists between two variables in a graph ! Hope it's useful~

*1.   Note whether the line is straight. When two variables are in proportion, the line representing them will be straight. This means that the slope of the line is constant, or follows the equation\

*2.  Determine the y-intercept. The y-intercept is the point where the line crosses the y-axis. When two variables are directly proportional, when graphed their line will cross through the origin. The origin is at the point {(0,0)}, so the y-intercept of the line should be (0). If it isn’t, the variables are not directly proportional.**The y-axis is the vertical axis.

*3.  Find the coordinates of two points on the line. Compare the coordinates with each other, and determine whether each coordinate changed by the same factor.[6] That is, determine whether the constant ({k}) is the same for both the { x} and { y} values.For example, if the first point is {(1,3)}, and the second point is { (2,6)}, the x-coordinate changed by a factor of 2, since { 1(2)=2}. The y-coordinate also changed by a factor of 2, since { 3(2)=6}. Thus, you can confirm that the line represents two variables that are directly proportional.

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Information taken from the following web:
https://www.wikihow.com/Determine-Whether-Two-Variables-Are-Directly-Proportional#Using_a_Graph_sub