Which of the following is correct?
(a) (a - b)² = a² + 2ab - b²
(b) (a - b)² = a² - 2ab + b²
(c) (a - b)² = a² - b²
(d) (a + b)² = a² + 2ab - b²

Solution:

Correct option is (b) because,

(a - b)² =(a - b)(a - b)

Multiplying the polynomials using the distributive property we get

= a(a - b) - b( a - b)

= a² - ab - ba + b²

= a² - 2ab + b²

✦ Try this: Find (x - 4)² - (x + 4)².

Using the identities we get

(x - 4)² - (x + 4)²

= x² - 8x + 16 - (x² + 8x + 16)

= x² - 8x + 16 - x² - 8x - 16

= -16x

Thus (x - 4)² -(x + 4)² = -16x

☛ Also Check: NCERT Solutions for Class 8 Maths Chapter 9

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NCERT Exemplar Class 8 Maths Chapter 7 Problem 3

Which of the following is correct? (a) (a - b)² = a² + 2ab - b² (b) (a - b)² = a² - 2ab + b² (c) (a - b)² = a² - b² (d) (a + b)² = a² + 2ab - b²

Summary:

(a - b)² = a² - 2ab + b² is correct

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☛ Related Questions:

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• Like term as 4m³n² is (a) 4m²n² (b) – 6m³n² (c) 6pm³n² (d) 4m³n