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Substituting into expressions

Substituting into expressions. Substitution. What does substitution mean?. In algebra, when we replace letters in an expression or equation with numbers we call it substitution. Substitution. 4 + 3 ×. How can be written as an algebraic expression?.

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Substituting into expressions

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  1. Substituting into expressions

  2. Substitution What doessubstitutionmean? In algebra, when we replace letters in an expression or equation with numbers we call it substitution.

  3. Substitution 4 + 3 × How can be written as an algebraic expression? Using n for the variable we can write this as 4 + 3n. We can evaluate the expression 4 + 3n by substituting different values for n. 4 + 3 ×5 When n = 5 4 + 3n = = 4 + 15 = 19 4 + 3 ×11 When n = 11 4 + 3n = = 4 + 33 = 37

  4. Substitution 7 × 7n 2 2 7n We can evaluate the expression by substituting different values for n. 2 7n = 2 7n = 2 can be written as 7 ×4 ÷ 2 When n = 4 = 28 ÷ 2 = 14 7 ×1.1 ÷ 2 When n = 1.1 = 7.7 ÷ 2 = 3.85

  5. Substitution 2 + 6 can be written as n2 + 6 We can evaluate the expressionn2 + 6 by substitutingdifferent values for n. 42 + 6 When n = 4 n2 + 6 = = 16 + 6 = 22 0.62 + 6 When n = 0.6 n2 + 6 = = 0.36 + 6 = 6.36

  6. Substitution 2( + 8) can be written as 2(n + 8) We can evaluate the expression 2(n + 8) by substitutingdifferent values for n. 2(n + 8) = 2 × (6 + 8) When n = 6 = 2 × 14 = 28 2(n + 8) = 2 × (13 + 8) When n = 13 = 2 × 21 = 42

  7. Substitution exercise 22 – –1 b2 – c = 5) a 5 Here are five expressions. 1) a + b + c =5 + 2 + –1 = 6 2) 3a + 2c = 3 ×5 + 2 ×–1 = 15 + –2 = 13 3) a(b + c) =5× (2 + –1) = 5 × 1 = 5 4) abc = 5×2×–1 = 10 ×–1 = –10 = 5 ÷ 5 = 1 Evaluate these expressions when a = 5, b = 2 and c = –1.

  8. Now try these:

  9. Answers: 11. 24 12. 13 13. 3 14. -1 15. 17 16. -9 17. 30 18. 10 19. 3 20. -3 21. 45 22. 23 23. 41 24. 9 25. 4 26. 8 27. 21 28. -12 29. 14 30. 27 31. -7 32. 8 33. 9 34. 25

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