Depth of rxy Value: In Case rxy Value = 0.00

If calculating the value of r_xy yields 0.00, then X and Y are definitely not linearly correlated. And if these ordered pairs are graphed into rectangular coordinate, they will always look like a symmetrical figure of 1 axis or 2 axes that are parallel to the X axis or the Y axis or both. And if the ordered pairs that are in the same straight line are parallel to only the X axis or Y axis, it will not be able to show how to calculate the r_xy value which, by the above principles, must be equal to 0.00. The reason is that when we substitute the values from the ordered pairs that are in the same straight line into the formula of r_xy, then the denominator of the formula is 0. So it can be said that it is difficult to explain.

What is more difficult to understand is the general transformation of a two-variable linear equation, Ax + By + C = 0, into a predictive equation, namely y =  or y = bx + a, whether or not the value is 0.00. To explain this, the aforementioned issue should be divided into 4 cases as follows:

Case 1: If A, B and C ≠ 0, the graph will have a slope such as Ax + By + C = 0 or y = bx + a. Example: -3x + 2y - 6 = 0 or y =

Case 2: If A or B ≠ 0 but C = 0, the graph will have a slope such as Ax + By + 0 = 0 or y = bx. Examples: -3x + 2y = 0 or y =

Case 3: If A or B = 0 and C = 0, the graph which is the X axis (if A = 0) or the Y axis (if B = 0) then has no slope such as (0)x + By + 0 = 0 or y = 0. Examples: (0)x + 5y = 0 or y = 0.

Case 4: If A or B = 0 but C ≠ 0, the graph is parallel to the X or the Y axis, so there is no slope such as (0) x + By + C = 0 or y = (0) x + C. Examples: (0)x - 4y +12 = 0 or y = 3

In case 4, learners are confused and do not understand the reason for the form of these equations because the explanation lacks the use of equation in the form of y =  , given A = 0 or from the example of real equation: y = etc.