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Class 8 Maths Worksheet: Algebraic Identities

Maths worksheets lesson 61: Algebraic identities · Set 421 · 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 39² − 35².
  2. 2.Use (a + b)² = a² + 2ab + b² to find 75².
  3. 3.Find the value of x² − 2xy + y² when x = 14 and y = 2.
  4. 4.Use a² − b² = (a + b)(a − b) to find 26² − 18².
  5. 5.Use (a + b)² = a² + 2ab + b² to find 33².
  6. 6.Use (a − b)² = a² − 2ab + b² to find 12².
  7. 7.Use (a + b)(a − b) = a² − b² to find 105 × 95.
  8. 8.Use a² − b² = (a + b)(a − b) to find 63² − 11².
  9. 9.Use (a + b)(a − b) = a² − b² to find 37 × 23.
  10. 10.Use (a + b)² = a² + 2ab + b² to find 48².
  11. 11.Use (a + b)(a − b) = a² − b² to find 92 × 88.
  12. 12.Use (a + b)² = a² + 2ab + b² to find 85².
  13. 13.If a + b = 6 and ab = 8, what is a² + b²?
  14. 14.Use (a − b)² = a² − 2ab + b² to find 17².
  15. 15.Use (a + b)(a − b) = a² − b² to find 76 × 64.
  16. 16.If a + b = 5 and ab = 4, what is a² + b²?
  17. 17.Use a² − b² = (a + b)(a − b) to find 32² − 25².
  18. 18.Find the value of x² + 2xy + y² when x = 4 and y = 3.
  19. 19.Find the value of x² + 2xy + y² when x = 9 and y = 2.
  20. 20.Use (a + b)² = a² + 2ab + b² to find 97².
  21. 21.If a − b = 6 and ab = 16, what is a² + b²?
  22. 22.Use (a + b)² = a² + 2ab + b² to find 86².
  23. 23.Use (a + b)² = a² + 2ab + b² to find 32².
  24. 24.Use a² − b² = (a + b)(a − b) to find 36² − 5².
  25. 25.If a − b = 2 and ab = 3, what is a² + b²?
  26. 26.Use (a − b)² = a² − 2ab + b² to find 81².
  27. 27.Use a² − b² = (a + b)(a − b) to find 36² − 18².
  28. 28.Use (a + b)(a − b) = a² − b² to find 72 × 68.
  29. 29.Use (a + b)(a − b) = a² − b² to find 41 × 39.
  30. 30.Find the value of x² − 2xy + y² when x = 3 and y = 2.
  31. 31.Find the value of x² − 2xy + y² when x = 13 and y = 2.
  32. 32.Use (a + b)² = a² + 2ab + b² to find 105².
  33. 33.Use (a + b)² = a² + 2ab + b² to find 84².
  34. 34.Use (a + b)² = a² + 2ab + b² to find 18².
  35. 35.Use a² − b² = (a + b)(a − b) to find 74² − 19².
  36. 36.Use a² − b² = (a + b)(a − b) to find 53² − 3².
  37. 37.Use (a − b)² = a² − 2ab + b² to find 67².
  38. 38.Use (a + b)² = a² + 2ab + b² to find 71².
  39. 39.Use (a + b)² = a² + 2ab + b² to find 93².
  40. 40.Use (a − b)² = a² − 2ab + b² to find 31².

Answer key

  1. 296
  2. 5625
  3. 144
  4. 352
  5. 1089
  6. 144
  7. 9975
  8. 3848
  9. 851
  10. 2304
  11. 8096
  12. 7225
  13. 20
  14. 289
  15. 4864
  16. 17
  17. 399
  18. 49
  19. 121
  20. 9409
  21. 68
  22. 7396
  23. 1024
  24. 1271
  25. 10
  26. 6561
  27. 972
  28. 4896
  29. 1599
  30. 1
  31. 121
  32. 11025
  33. 7056
  34. 324
  35. 5115
  36. 2800
  37. 4489
  38. 5041
  39. 8649
  40. 961

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