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Class 8 Maths Worksheet: Algebraic Identities

Maths worksheets lesson 61: Algebraic identities · Set 133 · 40 sums
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The method (Split into easy parts): (a + b)² = a² + 2ab + b². (a − b)² = a² − 2ab + b². (a + b)(a − b) = a² − b²; so a² − b² = (a + b)(a − b). a² + b² = (a + b)² − 2ab = (a − b)² + 2ab.

NameDateTime takenScore ___ / 40
  1. 1.Use (a − b)² = a² − 2ab + b² to find 26².
  2. 2.Use (a − b)² = a² − 2ab + b² to find 47².
  3. 3.If a − b = 6 and ab = 16, what is a² + b²?
  4. 4.If a + b = 14 and ab = 40, what is a² + b²?
  5. 5.Use (a + b)² = a² + 2ab + b² to find 93².
  6. 6.Use a² − b² = (a + b)(a − b) to find 91² − 65².
  7. 7.Use (a + b)² = a² + 2ab + b² to find 39².
  8. 8.If a + b = 12 and ab = 32, what is a² + b²?
  9. 9.Use (a − b)² = a² − 2ab + b² to find 41².
  10. 10.Use (a + b)(a − b) = a² − b² to find 46 × 34.
  11. 11.Use (a + b)² = a² + 2ab + b² to find 101².
  12. 12.Use (a + b)(a − b) = a² − b² to find 23 × 17.
  13. 13.If a + b = 5 and ab = 6, what is a² + b²?
  14. 14.If a + b = 4 and ab = 3, what is a² + b²?
  15. 15.Use (a + b)² = a² + 2ab + b² to find 51².
  16. 16.Use a² − b² = (a + b)(a − b) to find 91² − 84².
  17. 17.Use (a − b)² = a² − 2ab + b² to find 19².
  18. 18.Find the value of x² − y² when x = 15 and y = 10.
  19. 19.Use a² − b² = (a + b)(a − b) to find 77² − 41².
  20. 20.Use (a + b)² = a² + 2ab + b² to find 61².
  21. 21.Use (a + b)(a − b) = a² − b² to find 79 × 61.
  22. 22.Use a² − b² = (a + b)(a − b) to find 43² − 1².
  23. 23.Use (a + b)² = a² + 2ab + b² to find 54².
  24. 24.Use (a + b)(a − b) = a² − b² to find 26 × 14.
  25. 25.Find the value of x² − y² when x = 9 and y = 3.
  26. 26.Use (a + b)(a − b) = a² − b² to find 88 × 72.
  27. 27.Find the value of x² − 2xy + y² when x = 9 and y = 6.
  28. 28.Use (a − b)² = a² − 2ab + b² to find 55².
  29. 29.Use (a + b)(a − b) = a² − b² to find 107 × 93.
  30. 30.Use (a + b)² = a² + 2ab + b² to find 18².
  31. 31.If a + b = 21 and ab = 108, what is a² + b²?
  32. 32.Use (a + b)(a − b) = a² − b² to find 48 × 32.
  33. 33.If a + b = 9 and ab = 20, what is a² + b²?
  34. 34.Use (a − b)² = a² − 2ab + b² to find 15².
  35. 35.If a + b = 18 and ab = 72, what is a² + b²?
  36. 36.Use (a − b)² = a² − 2ab + b² to find 45².
  37. 37.Use a² − b² = (a + b)(a − b) to find 53² − 8².
  38. 38.If a − b = 1 and ab = 2, what is a² + b²?
  39. 39.Use (a + b)² = a² + 2ab + b² to find 36².
  40. 40.Use (a + b)² = a² + 2ab + b² to find 73².

Answer key

  1. 676
  2. 2209
  3. 68
  4. 116
  5. 8649
  6. 4056
  7. 1521
  8. 80
  9. 1681
  10. 1564
  11. 10201
  12. 391
  13. 13
  14. 10
  15. 2601
  16. 1225
  17. 361
  18. 125
  19. 4248
  20. 3721
  21. 4819
  22. 1848
  23. 2916
  24. 364
  25. 72
  26. 6336
  27. 9
  28. 3025
  29. 9951
  30. 324
  31. 225
  32. 1536
  33. 41
  34. 225
  35. 180
  36. 2025
  37. 2745
  38. 5
  39. 1296
  40. 5329

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