Slide 1: Lessons from the Math Zone: Variables Click to Start Lesson
Slide 2: Lessons from
the
Math Zone Variables © Copyright 2006, Don Link
Permission Granted for Educational Use Only
Slide 3: Variables Vary x = 5 7 6 8 9 10 10 15 20 25 30 40 50 100 200 300 1,000 2,000 3,000 4,000 5,000 1.0 1.1 1.2 1.3 1.4 1.5 2.5 3.5 4.5 5.5 5.5 0.01 0.02 3.33 –1 –2 –3 –4 –5 –1.5 –2.6 –3.7 –4.8 –5.9 –6.0
Slide 4: Algebraic Expressions An Algebraic Expression is an expression that contains at least one Variable. x + 14 3x + 1 9 – x
Slide 5: 9 – Using Variables x = + 14 3 + 1 =22 =25 x x =1 x =2 x One way to use variables is to substitute their numerical value into an algebraic expression. (8) (8) (8) (8) 8
Slide 6: 9 – One way to use variables is to substitute their numerical value into an algebraic expression Using Variables x = 8 + 14 3 + 1 =22 =25 x x =1 x =2 x Way to Go!
Slide 7: Let’s Practice x – 3 = 1 x = 4 2x – 3 = 5 9x + 3 = 39 10 – 2x = 2 x + x = 8 x ÷ 2 = 2 2(x + 5) = 18 (x +10)×(x – 2) = 28 3x + 4x – 2 = 26 5x = 20
Slide 8: Let’s Practice x – 3 = 1 x = 4 2x – 3 = 5 9x + 3 = 39 10 – 2x = 2 x + x = 8 x ÷ 2 = 2 2(x + 5) = 18 (x +10)×(x – 2) = 28 3x + 4x – 2 = 26 5x = 20 High Five!
Slide 9: Let’s Practice with Two Variables a+b–2 = 6 a = 3 2b – 3a = 1 5a ÷ b = 3 ab = 15 a(b + 5) = 30 (a +10)×(b – 2) = 39 3ab + 4a – 2 = 55 5a–b = 10 b = 5
Slide 10: Let’s Practice with Two Variables a+b–2 = 6 a = 3 2b – 3a = 1 5a ÷ b = 3 ab = 15 a(b + 5) = 30 (a +10)×(b – 2) = 39 3ab + 4a – 2 = 55 5a–b = 10 b = 5 Good Job!
Slide 11: Another way to use a variable is as an unknown value in an algebraic equation. Unknown Variables 5 + x = 8 An Equation Claims that the Left Side = the Right Side Unknown Left
Side Right
Side
Slide 12: Unknown Variables 5 + x = 8 An Equation If: Left Side Right Side, = then the “equation is .” true If: Left Side Right Side, ≠ then the “equation is .” false To find the unknown value that makes the equation true, we “solve the equation for x.”
Slide 13: 5 + = 8 If x = 7 , the equation is 7 Unknown Variables True? False? True? False? x 12 8 3 If x = 3 , the equation is = 8
Slide 14: Solving an Equation Solving an equation means finding a value for the unknown that makes the equation true. 5 + x = 8 What value for x will make this equation true? 3 is a solution to the equation.
Slide 15: Let’s Practice Using Different Variables x – 3 = 10 4w – 3 = 5 2δ ÷ 3 = 6 20 – □ = 2 5a = 20 x = 13 a = 4 w = 2 δ = 9 □ = 18
Slide 16: Let’s Practice Using Different Variables x – 3 = 10 4w – 3 = 5 2δ ÷ 3 = 6 20 – □ = 2 5a = 20 x = 13 a = 4 w = 2 δ = 9 □ = 18 Cookin’!
Slide 17: x + 17 = 25 8 x = 8 x – 3 = 4 Variables: Summary and Review 1 Substitute the numerical value of a variable into an algebraic expression 2 “Solve the equation for x.” x = 4 1
Slide 18: For Printing