Lesson 4.3Topic/ Objective: To interpret and graph proportional relationships.

Essential Question: What are the characteristics of a proportional relationship graph?

ALL PROPORTIONAL RELATIONSHIPS ARE IN

THE FORM OF y = mx

Direct Variation: All proportional relationships are called a Direct variation y = mx where y varies directly to x. m represents the slope/constant of proportionality.

All direct variation graphs pass through the origin

Graph y = 2x

x y

-2

-1

0

1

2

-4

-2

0

2

4

The weight y of an object on Titan, one of Saturn’s moons, is proportional to the weight x of the object on Earth. An object that weighs 105 pounds on Earth would weigh 15 pounds on Titan

a. Write an equation that represents the situation.

Use the point (105, 15) to find the slope of the line.

y = mx15 = m(105)