The direct variation.

The video tutorial explains the concept of variation using an equilateral triangle. It demonstrates how the perimeter of the triangle changes with different side lengths and establishes a constant ratio of perimeter to side length. The tutorial concludes with a graphical representation of this relationship, showing it as a straight line through the origin.

What is the perimeter of an equilateral triangle when the length of its side is 1?

If the side length x of an equilateral triangle is 2, what is the perimeter?

What happens to the perimeter of an equilateral triangle as the side length x increases?

Explain the relationship between the perimeter (p) and the side length (x) of an equilateral triangle.

Describe the graphical representation of the relationship between perimeter and side length for an equilateral triangle.