So only first equation. The number k is called the constant of proportionality or constant of variation. For example if y varies directly as x and y 6 when x 2 the constant of variation is k 3.
A direct variation is a linear equation that can be written in the form y kx where k is a nonzero constant.
Since k is constant the same for every point we can find k when given any point by dividing the y-coordinate by the x-coordinate. And it always doesnt have to be y and x. Since k is constant the same for every point we can find k when given any point by dividing the y-coordinate by the x-coordinate. Think of it as the Slope-Intercept Form of a line written as y mx b y mx b where b 0 b 0.