To show that the ratio is not constant for the function we only need to evaluate this function at 2 points and then show that the ratio is not the same for those two points. Note that here represents .
To find the counter examples here, I will use the values and . For , the equation tells us that the output is
. For this value of the point is point is . The ratio . For the , . For this value of the point is . The ratio . Clearly this ratio is not constant for all ordered pairs.