1. Unit 1: Number Sense Minds On

2. Unit 1: Number Sense Lesson 7 - Substitution Learning Goal I can evaluate expressions containing variables by substituting in numbers for the variables.

3. Unit 1: Number Sense Lesson 7 - Substitution What is a variable? It is a symbol, usually a letter, that represents some quantity in an expression or equation. The variable could be one of many numbers.

4. Unit 1: Number Sense Lesson 7 - Substitution Sometimes there is only one possible value for the variable: 7 – x = 3

5. Unit 1: Number Sense Lesson 7 - Substitution Sometimes there are two possible values for the variable: (x – 8) 2 = 9

6. Unit 1: Number Sense Lesson 7 - Substitution Sometimes there are many possible values for the variable: x + y = 10

7. Unit 1: Number Sense Lesson 7 - Substitution What is the difference between an expression and an equation?

8. Unit 1: Number Sense Lesson 7 - Substitution What does an equal sign mean?

9. Unit 1: Number Sense Lesson 7 - Substitution Consider this expression: 5x + 8 What does it mean? What could “x” be?

10. Unit 1: Number Sense Lesson 7 - Substitution Consider this expression: 5x + 8 What if I tell you x = (-2)? Can you rewrite the expression? Can you simplify it?

11. Unit 1: Number Sense Lesson 7 - Substitution Example: Evaluate the expression for x = 4: -3(5x – 7)

12. Unit 1: Number Sense Lesson 7 - Substitution Example: Evaluate the expression for x = 4: -0.5(x – 2) + 4x

13. Unit 1: Number Sense Lesson 7 - Substitution Remember, BEDMAS still applies when you are evaluating expressions by substituting in values for variables.

14. Unit 1: Number Sense Lesson 7 - Substitution

15. Unit 1: Number Sense Lesson 7 - Substitution Example: Evaluate the expression for z = 6 5(z 2 ) + (z – 3) 2 + (3z – 1)(2z)

16. Unit 1: Number Sense Lesson 7 - Substitution Always substitute in with brackets… x = -4 Evaluate: 2x – x + x 2

17. Unit 1: Number Sense Lesson 7 - Substitution Can we have more than one variable?

18. Unit 1: Number Sense Lesson 7 - Substitution Example: Evaluate the expression for: a = 1, b = 2, c = 3 -2(a-b) 2 + ac – (a + b-c)

19. Unit 1: Number Sense Lesson 7 - Substitution

20. Unit 1: Number Sense Lesson 7 - Substitution Practice  Page 17 Q# 10 and Page 194 Q# 6  Handout: “DID YOU HEAR ABOUT…”  Quiz Tomorrow