Question

(a+b) (a-b) = ?
what is the answer
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Answer 1

Answer- The above question is from the chapter 'Algebraic Expressions'.

Important identities:

1) (a+b)² = a² + 2ab + b²

2) (a-b)² = a² - 2ab + b²

Given question: What is the answer of (a+b) (a-b) ?

Solution: Let's multiply to get the answer.

(a+b) (a-b)

= a² + ab - ab - b²

= a² - b²

∴ The third algebraic identity is (a+b) (a-b)= a² - b².

Let's take an example of (2+3) (2-3).

This is in the form (a+b) (a-b) where a= 2 and b= 3. By using identity of (a+b) (a-b)= a² - b²,

(2+3) (2-3)= 2² - 3²

               = 4 - 9

               = -5

If we check this by simple calculation,

(2+3) (2-3)= 5 × -1 = -5

∴(a+b) (a-b)= a² - b².