What is Direct Variation?

"A relationship between two variables in which one is a constant multiple of the other. In particular, when one variable changes the other changes in proportion to the first.

If b is directly proportional to a, the equation is of the form b = ka (where k is a constant).

Equation: y = 4x

Variable y is directly proportional to x.

Doubling x causes y to double. Tripling x causes y to triple.

x y

1 4

2 8

3 12"