Let us discuss some algebra identities and do its formula.

  • Identity I - (a + b) 2 = a 2 + b 2 + 2ab
  • Identity II - (a − b) 2 = a 2 + b 2 − 2ab
  • Identity III - a 2 − b 2 = (a − b) (a + b)
  • Identity IV -   (x + a) (x + b) = x 2 + (a + b) x + ab

 

See Algebra Formulas for full list of identities.

 

Let’s take examples of the identities

Identity I - (a + b) 2 = a 2 + b 2 + 2ab

(2 + 3) 2 = 22 + 32 + 2(2)(3)

52 = 4 + 9 + 12

25 = 25


Identity II - (a − b) 2 = a 2 + b 2 − 2ab

(2 – 3) 2 = 2 2 + 3 2 – 2(2)(3)

(–1) 2 = 4 + 9 – 12

1 = 13 – 12

1 = 1


Identity III - a 2 − b 2 = (a − b) (a + b)

2 2 – 3 2 = (2 – 3) (2 + 3)

4 – 9 = – 1  × 5

–5 = –5


Identity IV -   (x + a) (x + b) = x 2 + (a + b) x + ab

(10 + 2) (10 + 3) = 102 + (2 + 3)10 + 2 × 3

12 ×  13 = 100 + 5 × 10 + 6

156 = 100 + 50 + 6

156 = 156

  1. Chapter 2 Class 9 Polynomials
  2. Concept wise
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Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 7 years. He provides courses for Mathematics and Science from Class 6 to 12. You can learn personally from here https://www.teachoo.com/premium/maths-and-science-classes/.
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