1. Warm Up 1) Find the slope of a line that goes through the points (-3, 5) and (11, -2) 2) Write the equation of a horizontal line that goes through the point (-3, 5) 3) What is the slope of this line?

2. HW Check 4.2

3. Direct Variation

4. A linear function defined by an equation of the form y = kx, where k ≠ 0, represents direct variation.

5. Constant of Variation The Slope, k, is constant. It can be represented at the ratio of

6. Identifying Direct Variation from a Table Determine whether y varies directly with x. If so, find the constant of variation and write the equations. 1. 2. XY 28 312 520 XY 14 27 516

7. Try Some!! Determine whether y varies directly with x. If so, find the constant of variation and write the equations. 1. 2. XY -2 34 67 XY -6-2 31 124

8. Identifying Direct Variation from an Equation For each function, determine whether y varies directly with x. If so, Find the constant of variation. 1. y = 4x 2. 2y = 3x 3. y = 2x + 3

9. Try Some!! Determine whether y varies directly with x. If so, find the constant of variation. 1. y = x/2 2. 2y – 1 = x 3. 4x = 8y 4. 7x + 4y = 10

10. Using Proportions If we know that y varies directly with x. We can use proportions to find missing information. Ex. Suppose y varies directly with x, and x = 3 when y = 7. Find x when y = 21.

11. Word Problems A dripping faucet wastes a cup of water if it drips for three minutes. The amount of water wasted varies directly with the amount of time the faucet drips. Find the constant of variation, and write an equation.

12. Word Problems The Height of an object varies directly with the length of its shadow. A person 6 ft tall casts an 8.5 ft shadow, while a tree casts a 38 ft shadow. How tall is the tree?

13. Coming up… HW 4.3 QUIZ tomorrow!