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Class 8 Maths Worksheet: Algebraic Identities

Maths worksheets lesson 61: Algebraic identities · Set 381 · 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.Find the value of x² − y² when x = 12 and y = 2.
  2. 2.Use (a + b)² = a² + 2ab + b² to find 66².
  3. 3.Use a² − b² = (a + b)(a − b) to find 21² − 11².
  4. 4.Use (a + b)(a − b) = a² − b² to find 51 × 49.
  5. 5.If a + b = 3 and ab = 2, what is a² + b²?
  6. 6.Use (a + b)² = a² + 2ab + b² to find 105².
  7. 7.If a − b = 6 and ab = 55, what is a² + b²?
  8. 8.Find the value of x² + 2xy + y² when x = 7 and y = 3.
  9. 9.Find the value of x² + 2xy + y² when x = 3 and y = 1.
  10. 10.Use a² − b² = (a + b)(a − b) to find 43² − 12².
  11. 11.If a − b = 1 and ab = 30, what is a² + b²?
  12. 12.Find the value of x² + 2xy + y² when x = 14 and y = 3.
  13. 13.If a + b = 6 and ab = 8, what is a² + b²?
  14. 14.Use a² − b² = (a + b)(a − b) to find 77² − 14².
  15. 15.Use a² − b² = (a + b)(a − b) to find 90² − 80².
  16. 16.Use (a − b)² = a² − 2ab + b² to find 47².
  17. 17.Use a² − b² = (a + b)(a − b) to find 43² − 23².
  18. 18.Use (a + b)(a − b) = a² − b² to find 53 × 47.
  19. 19.Use (a − b)² = a² − 2ab + b² to find 55².
  20. 20.Use (a − b)² = a² − 2ab + b² to find 91².
  21. 21.If a − b = 2 and ab = 3, what is a² + b²?
  22. 22.Find the value of x² − y² when x = 11 and y = 3.
  23. 23.Use (a + b)(a − b) = a² − b² to find 105 × 95.
  24. 24.Use (a + b)² = a² + 2ab + b² to find 58².
  25. 25.Use (a + b)² = a² + 2ab + b² to find 37².
  26. 26.Find the value of x² − 2xy + y² when x = 7 and y = 5.
  27. 27.Find the value of x² + 2xy + y² when x = 6 and y = 4.
  28. 28.Use (a + b)² = a² + 2ab + b² to find 11².
  29. 29.Use (a + b)² = a² + 2ab + b² to find 44².
  30. 30.If a − b = 2 and ab = 15, what is a² + b²?
  31. 31.Use (a − b)² = a² − 2ab + b² to find 52².
  32. 32.If a + b = 12 and ab = 32, what is a² + b²?
  33. 33.Find the value of x² + 2xy + y² when x = 7 and y = 6.
  34. 34.Use (a − b)² = a² − 2ab + b² to find 24².
  35. 35.Use (a + b)(a − b) = a² − b² to find 49 × 31.
  36. 36.Use (a + b)(a − b) = a² − b² to find 47 × 33.
  37. 37.Use (a + b)² = a² + 2ab + b² to find 72².
  38. 38.Use (a − b)² = a² − 2ab + b² to find 39².
  39. 39.Use a² − b² = (a + b)(a − b) to find 42² − 6².
  40. 40.Use (a + b)² = a² + 2ab + b² to find 97².

Answer key

  1. 140
  2. 4356
  3. 320
  4. 2499
  5. 5
  6. 11025
  7. 146
  8. 100
  9. 16
  10. 1705
  11. 61
  12. 289
  13. 20
  14. 5733
  15. 1700
  16. 2209
  17. 1320
  18. 2491
  19. 3025
  20. 8281
  21. 10
  22. 112
  23. 9975
  24. 3364
  25. 1369
  26. 4
  27. 100
  28. 121
  29. 1936
  30. 34
  31. 2704
  32. 80
  33. 169
  34. 576
  35. 1519
  36. 1551
  37. 5184
  38. 1521
  39. 1728
  40. 9409

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