1. Algebra 1(A/B) Mr. Valdez Fall 2012

2. Today’s Schedule  Minute Math Warm-Up  Return 3.4-3.6 Quizzes  3.7 Notes  Treasure Raffle Exit Slip  Begin Homework

3. 3.7 – Formulas and Functions  Objective  Solve a formula for one of its variables

4. What is a Formula?  Definition:  An algebraic __________ that relates two or more ___________ quantities.  Examples:  Area of rectangle  Temperature equation real-life A = l ∙ w C = 5/9 ∙ (F – 32)

5. Using the Area Formula  What is the area of a rectangle with…  l = 5 cm, w = 12 cm  l = 7 ft, w = 9 ft  l = 3 cm, w = 13 cm 60 cm 2 63 cm 2 39 cm 2 A = l ∙ w Notice: We were given a length and width.

6. Using the Area Formula  What is the length of a rectangle with an area of 228 cm 2 and a width of 12 cm?  Turn to your partner and figure out a solution. l = 19 cm A = l ∙ w Notice: We are given a different set of information in this problem.

7. Try to Solve for the Length  We want the equation to say “ l equals…”  Think: A = l ∙ w How do I get l by itself?

8. Try to Solve for the Length  Perform the inverse operations to isolate the variable. A = l ∙ w l = (A/w)

9. Solving for Length  Use this new formula to solve for length.  A = 49 cm 2, w = 7 cm  A = 108 ft 2, w = 12 ft  A = 36 cm 2, w = 9 cm 7 cm 9 cm 4 cm l = (A/w)

10. Using the Distance Formula d = r ∙ t  Solve the distance formula for time (t).  The equation should say “t equals…”  Solve the distance formula for the rate (r).  The equation should say “r equals…” t = (d/r) r = (d/t)

11. Did You Know… That the number of chirps a cricket makes per minute is related to what the temperature is outside?

12. Formula n = number of chirps per minute F = temperature (in Fahrenheit) F = (n/4) + 40 Suppose that we wanted to figure out the number of chirps given a certain temperature. We need to solve for n.

13. Solve the Formula for n If the temperature is 80 °F outside, how many chirps are the crickets making per minute? F = (n/4) + 40 160 chirps per minute

14. 2-3 Minute Break  Use this time to relax, stretch out, or talk to a neighbor.  Return to your seat and quiet down immediately after the break ends. What is represented by this brain puzzle? H I J K L M N O

15. Rewrite the equation so that y is a function of x. 1) 15x + 5y = 10 2) 1 + 7y = 5x – 2 3) 7x + 5x = -8 + 2y

16. Rewrite the equation so that y is a function of x. 1) 3(x – 2) = 2y 2) (y/5) – 7 = -2x 3) 13 = 12x – 2y

17. Treasure Raffle Exit Slip Rewrite the equation so that y is a function of x. (Solve for y.) 1) 16x – 4 = 4y 2) (y/2) – 5 = -3x 3) 6 = 10x + 3y Homework Assignment: pg. 177 #11, 12, 15, 24, 26, 28