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Class 8 Maths Worksheet: Algebraic Identities

Maths worksheets lesson 61: Algebraic identities · Set 206 · 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 36² − 3².
  2. 2.Use a² − b² = (a + b)(a − b) to find 30² − 7².
  3. 3.If a + b = 16 and ab = 55, what is a² + b²?
  4. 4.If a − b = 1 and ab = 2, what is a² + b²?
  5. 5.If a + b = 10 and ab = 16, what is a² + b²?
  6. 6.Find the value of x² − y² when x = 15 and y = 13.
  7. 7.Use (a + b)² = a² + 2ab + b² to find 21².
  8. 8.Use (a − b)² = a² − 2ab + b² to find 95².
  9. 9.If a − b = 5 and ab = 6, what is a² + b²?
  10. 10.Use (a − b)² = a² − 2ab + b² to find 89².
  11. 11.If a + b = 5 and ab = 4, what is a² + b²?
  12. 12.Use a² − b² = (a + b)(a − b) to find 45² − 24².
  13. 13.Use (a + b)(a − b) = a² − b² to find 38 × 22.
  14. 14.Use (a − b)² = a² − 2ab + b² to find 91².
  15. 15.Use (a − b)² = a² − 2ab + b² to find 19².
  16. 16.Find the value of x² − y² when x = 8 and y = 2.
  17. 17.Use (a − b)² = a² − 2ab + b² to find 43².
  18. 18.If a − b = 11 and ab = 12, what is a² + b²?
  19. 19.Find the value of x² − y² when x = 14 and y = 2.
  20. 20.Use (a + b)(a − b) = a² − b² to find 48 × 32.
  21. 21.If a + b = 12 and ab = 27, what is a² + b²?
  22. 22.Use (a + b)² = a² + 2ab + b² to find 108².
  23. 23.Use (a + b)(a − b) = a² − b² to find 61 × 59.
  24. 24.Use (a − b)² = a² − 2ab + b² to find 45².
  25. 25.Use (a + b)(a − b) = a² − b² to find 84 × 76.
  26. 26.Use a² − b² = (a + b)(a − b) to find 25² − 8².
  27. 27.Find the value of x² − y² when x = 4 and y = 3.
  28. 28.Use (a − b)² = a² − 2ab + b² to find 11².
  29. 29.Use a² − b² = (a + b)(a − b) to find 28² − 12².
  30. 30.If a − b = 2 and ab = 35, what is a² + b²?
  31. 31.Use (a + b)(a − b) = a² − b² to find 75 × 65.
  32. 32.Use (a + b)(a − b) = a² − b² to find 21 × 19.
  33. 33.Use (a + b)² = a² + 2ab + b² to find 44².
  34. 34.Use (a + b)² = a² + 2ab + b² to find 38².
  35. 35.If a + b = 5 and ab = 6, what is a² + b²?
  36. 36.Use a² − b² = (a + b)(a − b) to find 38² − 11².
  37. 37.If a + b = 8 and ab = 7, what is a² + b²?
  38. 38.Use a² − b² = (a + b)(a − b) to find 34² − 3².
  39. 39.If a + b = 13 and ab = 12, what is a² + b²?
  40. 40.Use (a − b)² = a² − 2ab + b² to find 29².

Answer key

  1. 1287
  2. 851
  3. 146
  4. 5
  5. 68
  6. 56
  7. 441
  8. 9025
  9. 37
  10. 7921
  11. 17
  12. 1449
  13. 836
  14. 8281
  15. 361
  16. 60
  17. 1849
  18. 145
  19. 192
  20. 1536
  21. 90
  22. 11664
  23. 3599
  24. 2025
  25. 6384
  26. 561
  27. 7
  28. 121
  29. 640
  30. 74
  31. 4875
  32. 399
  33. 1936
  34. 1444
  35. 13
  36. 1323
  37. 50
  38. 1147
  39. 145
  40. 841

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