Algebra 1

Direct Variation

Day 10 Objective: 3.02

FormulaDirect Variation

y = kx, where k is a constant

An example of direct variation is how the weight of a package determines the cost to mail it.

For the data, tell if y varies directly with x.

7) 8)

X Y

-2 3.2

1 2.4

4 1.6

X Y

4 6

8 12

10 15

Examples9) If y varies directly

with x, and y = 18 when x = 12, what is the value of y when x = 5?

10) If y varies directly with x, and y = 45 when x = 2, what is the value of y when x = 5?

Examples11) A recipe for a dozen

corn muffins calls for 1 cup of flour. The number of muffins varies directly with the amount of flour. How many cups of flour are needed for 65 muffins?

12) A package weighs 19 oz. The cost to mail it is $6.84. The cost varies directly with the weight. How much will a 5 oz. package cost?

Example13) Suppose you walk 2

miles in 35 minutes. If the distance varies to the time, find how many miles you would walk in 60 minutes.

14) The stopping distance of a car after the brakes have been applied varies directly as the square of the speed. If a car traveling at 45mph can stop in 101.25ft, what is the distance needed to stop the same car traveling at 54mph?

Algebra 1

Slope intercept form

School Day 11 Objective: 3.03, 4.01

Slope-Intercept Form y=mx+b

m=slope (rise/run) b=y-intercept (where line crosses y-axis) y = -4x + 3 m=____b=____ y = -x – 7 m=____b=____ y = 3 + ¾x m=____b=____ y - 6 = ½x m=____b=____ m= -3 b= ¼ slope-int form:_____________

Find the slope and y-intercept of each equation.

8) y = -2x + 1 9) y = ½ x – 5

10) y = ⅝x 11) y = 5

Write an equation in slope-intercept form.

12) m = 3, b = 4 13) m = 0, b = -3

14) m = undefined, b = 4

m=movement b= beginning15) A cell phone company charges $.05 per

text and a base rate of $10 each month. Write an equation to model your monthly bill.

Write the equation of the line.16) 17)