Class 8 Maths Worksheet: Algebraic Identities
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.
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- 1.Find the value of x² + 2xy + y² when x = 14 and y = 11.
- 2.If a − b = 4 and ab = 5, what is a² + b²?
- 3.Use (a + b)² = a² + 2ab + b² to find 23².
- 4.Use (a − b)² = a² − 2ab + b² to find 39².
- 5.If a + b = 10 and ab = 16, what is a² + b²?
- 6.Use a² − b² = (a + b)(a − b) to find 70² − 51².
- 7.Use a² − b² = (a + b)(a − b) to find 31² − 11².
- 8.If a + b = 3 and ab = 2, what is a² + b²?
- 9.Use (a − b)² = a² − 2ab + b² to find 78².
- 10.Use (a − b)² = a² − 2ab + b² to find 84².
- 11.Use (a + b)² = a² + 2ab + b² to find 68².
- 12.Use (a − b)² = a² − 2ab + b² to find 26².
- 13.Use (a + b)(a − b) = a² − b² to find 85 × 75.
- 14.If a − b = 3 and ab = 10, what is a² + b²?
- 15.Use (a + b)² = a² + 2ab + b² to find 93².
- 16.Find the value of x² − 2xy + y² when x = 7 and y = 6.
- 17.If a + b = 4 and ab = 3, what is a² + b²?
- 18.If a − b = 1 and ab = 2, what is a² + b²?
- 19.If a − b = 4 and ab = 12, what is a² + b²?
- 20.Use (a − b)² = a² − 2ab + b² to find 37².
- 21.Use a² − b² = (a + b)(a − b) to find 75² − 1².
- 22.Use (a + b)(a − b) = a² − b² to find 74 × 66.
- 23.Use (a + b)² = a² + 2ab + b² to find 43².
- 24.Use (a + b)(a − b) = a² − b² to find 28 × 12.
- 25.Use (a + b)² = a² + 2ab + b² to find 103².
- 26.Use (a + b)(a − b) = a² − b² to find 32 × 28.
- 27.Use a² − b² = (a + b)(a − b) to find 74² − 13².
- 28.Use (a − b)² = a² − 2ab + b² to find 88².
- 29.Use a² − b² = (a + b)(a − b) to find 76² − 52².
- 30.Find the value of x² − 2xy + y² when x = 15 and y = 9.
- 31.If a + b = 11 and ab = 30, what is a² + b²?
- 32.If a − b = 3 and ab = 4, what is a² + b²?
- 33.Find the value of x² − y² when x = 14 and y = 9.
- 34.Find the value of x² − y² when x = 5 and y = 4.
- 35.Use (a − b)² = a² − 2ab + b² to find 86².
- 36.Use (a − b)² = a² − 2ab + b² to find 44².
- 37.Use (a − b)² = a² − 2ab + b² to find 79².
- 38.Use (a − b)² = a² − 2ab + b² to find 56².
- 39.If a − b = 7 and ab = 30, what is a² + b²?
- 40.Use (a + b)² = a² + 2ab + b² to find 67².
Answer key
- 625
- 26
- 529
- 1521
- 68
- 2299
- 840
- 5
- 6084
- 7056
- 4624
- 676
- 6375
- 29
- 8649
- 1
- 10
- 5
- 40
- 1369
- 5624
- 4884
- 1849
- 336
- 10609
- 896
- 5307
- 7744
- 3072
- 36
- 61
- 17
- 115
- 9
- 7396
- 1936
- 6241
- 3136
- 109
- 4489
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