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Class 8 Maths Worksheet: Algebraic Identities

Maths worksheets lesson 61: Algebraic identities · Set 755 · 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 31².
  2. 2.Use a² − b² = (a + b)(a − b) to find 65² − 56².
  3. 3.If a + b = 16 and ab = 63, what is a² + b²?
  4. 4.Find the value of x² − 2xy + y² when x = 5 and y = 1.
  5. 5.Use (a − b)² = a² − 2ab + b² to find 12².
  6. 6.Use (a + b)² = a² + 2ab + b² to find 75².
  7. 7.If a + b = 11 and ab = 10, what is a² + b²?
  8. 8.Use (a + b)² = a² + 2ab + b² to find 83².
  9. 9.Use a² − b² = (a + b)(a − b) to find 53² − 20².
  10. 10.Use a² − b² = (a + b)(a − b) to find 95² − 53².
  11. 11.Find the value of x² − y² when x = 9 and y = 2.
  12. 12.Find the value of x² − y² when x = 12 and y = 5.
  13. 13.Use a² − b² = (a + b)(a − b) to find 88² − 61².
  14. 14.Use (a + b)² = a² + 2ab + b² to find 81².
  15. 15.Use (a + b)(a − b) = a² − b² to find 35 × 25.
  16. 16.Use (a + b)² = a² + 2ab + b² to find 39².
  17. 17.Use a² − b² = (a + b)(a − b) to find 65² − 32².
  18. 18.Use a² − b² = (a + b)(a − b) to find 66² − 2².
  19. 19.Use (a + b)(a − b) = a² − b² to find 109 × 91.
  20. 20.Use a² − b² = (a + b)(a − b) to find 77² − 43².
  21. 21.Use (a + b)² = a² + 2ab + b² to find 106².
  22. 22.Use a² − b² = (a + b)(a − b) to find 43² − 8².
  23. 23.Use (a + b)(a − b) = a² − b² to find 93 × 87.
  24. 24.Use a² − b² = (a + b)(a − b) to find 33² − 18².
  25. 25.Use a² − b² = (a + b)(a − b) to find 86² − 58².
  26. 26.Find the value of x² − y² when x = 15 and y = 10.
  27. 27.Use (a + b)² = a² + 2ab + b² to find 14².
  28. 28.Use a² − b² = (a + b)(a − b) to find 43² − 40².
  29. 29.Find the value of x² − 2xy + y² when x = 3 and y = 2.
  30. 30.Use (a + b)(a − b) = a² − b² to find 76 × 64.
  31. 31.Find the value of x² + 2xy + y² when x = 8 and y = 6.
  32. 32.Find the value of x² + 2xy + y² when x = 11 and y = 1.
  33. 33.Use (a − b)² = a² − 2ab + b² to find 21².
  34. 34.If a + b = 3 and ab = 2, what is a² + b²?
  35. 35.Use (a + b)(a − b) = a² − b² to find 37 × 23.
  36. 36.Use (a − b)² = a² − 2ab + b² to find 31².
  37. 37.Use (a − b)² = a² − 2ab + b² to find 84².
  38. 38.Use (a + b)² = a² + 2ab + b² to find 59².
  39. 39.Use (a + b)² = a² + 2ab + b² to find 29².
  40. 40.Use (a + b)(a − b) = a² − b² to find 23 × 17.

Answer key

  1. 961
  2. 1089
  3. 130
  4. 16
  5. 144
  6. 5625
  7. 101
  8. 6889
  9. 2409
  10. 6216
  11. 77
  12. 119
  13. 4023
  14. 6561
  15. 875
  16. 1521
  17. 3201
  18. 4352
  19. 9919
  20. 4080
  21. 11236
  22. 1785
  23. 8091
  24. 765
  25. 4032
  26. 125
  27. 196
  28. 249
  29. 1
  30. 4864
  31. 196
  32. 144
  33. 441
  34. 5
  35. 851
  36. 961
  37. 7056
  38. 3481
  39. 841
  40. 391

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