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Class 8 Maths Worksheet: Algebraic Identities

Maths worksheets lesson 61: Algebraic identities · Set 184 · 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 a² − b² = (a + b)(a − b) to find 89² − 60².
  2. 2.Use a² − b² = (a + b)(a − b) to find 37² − 5².
  3. 3.Use (a + b)² = a² + 2ab + b² to find 81².
  4. 4.Use (a − b)² = a² − 2ab + b² to find 45².
  5. 5.Use a² − b² = (a + b)(a − b) to find 20² − 2².
  6. 6.Find the value of x² + 2xy + y² when x = 13 and y = 11.
  7. 7.Use (a + b)² = a² + 2ab + b² to find 97².
  8. 8.Use (a − b)² = a² − 2ab + b² to find 81².
  9. 9.Use (a + b)² = a² + 2ab + b² to find 47².
  10. 10.If a − b = 7 and ab = 30, what is a² + b²?
  11. 11.If a + b = 5 and ab = 4, what is a² + b²?
  12. 12.Use (a + b)² = a² + 2ab + b² to find 107².
  13. 13.If a − b = 4 and ab = 5, what is a² + b²?
  14. 14.Use a² − b² = (a + b)(a − b) to find 87² − 13².
  15. 15.Use (a + b)(a − b) = a² − b² to find 34 × 26.
  16. 16.Use (a − b)² = a² − 2ab + b² to find 35².
  17. 17.Use (a − b)² = a² − 2ab + b² to find 49².
  18. 18.Find the value of x² − y² when x = 10 and y = 1.
  19. 19.Use (a − b)² = a² − 2ab + b² to find 78².
  20. 20.Use (a + b)² = a² + 2ab + b² to find 102².
  21. 21.Use (a − b)² = a² − 2ab + b² to find 31².
  22. 22.Use (a + b)² = a² + 2ab + b² to find 87².
  23. 23.Use (a + b)² = a² + 2ab + b² to find 74².
  24. 24.Use (a + b)² = a² + 2ab + b² to find 51².
  25. 25.Use a² − b² = (a + b)(a − b) to find 93² − 21².
  26. 26.If a − b = 8 and ab = 9, what is a² + b²?
  27. 27.Use (a + b)(a − b) = a² − b² to find 54 × 46.
  28. 28.If a + b = 12 and ab = 35, what is a² + b²?
  29. 29.Use a² − b² = (a + b)(a − b) to find 65² − 16².
  30. 30.If a − b = 7 and ab = 18, what is a² + b²?
  31. 31.If a − b = 3 and ab = 10, what is a² + b²?
  32. 32.Use (a + b)² = a² + 2ab + b² to find 26².
  33. 33.Use (a + b)² = a² + 2ab + b² to find 31².
  34. 34.Use (a + b)² = a² + 2ab + b² to find 67².
  35. 35.Use a² − b² = (a + b)(a − b) to find 40² − 19².
  36. 36.Use (a − b)² = a² − 2ab + b² to find 62².
  37. 37.If a + b = 4 and ab = 3, what is a² + b²?
  38. 38.Use (a + b)² = a² + 2ab + b² to find 91².
  39. 39.Use a² − b² = (a + b)(a − b) to find 99² − 9².
  40. 40.Find the value of x² − 2xy + y² when x = 3 and y = 2.

Answer key

  1. 4321
  2. 1344
  3. 6561
  4. 2025
  5. 396
  6. 576
  7. 9409
  8. 6561
  9. 2209
  10. 109
  11. 17
  12. 11449
  13. 26
  14. 7400
  15. 884
  16. 1225
  17. 2401
  18. 99
  19. 6084
  20. 10404
  21. 961
  22. 7569
  23. 5476
  24. 2601
  25. 8208
  26. 82
  27. 2484
  28. 74
  29. 3969
  30. 85
  31. 29
  32. 676
  33. 961
  34. 4489
  35. 1239
  36. 3844
  37. 10
  38. 8281
  39. 9720
  40. 1

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