Question

What is that constant of proportionality in the equation?
y=4x

Answer 1

In a direct relationship, we have a value y that varies directly with x. We can write that
`(y)/(x)` is equal to the k, the constant of variation. This is the same as the slope, m, in a linear equation.

Here, 4 is the constant of variation. For some number x, y is four times that number—no matter what.