Practice Set 5.1 Expansion Formulae | Class 8 Maths English Medium | Maharashtra Board | Complete Solutions

Lesson 5 – Expansion Formulae | Practice Set 5.1

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In this post, you will find complete step-by-step solutions for Practice Set 5.1 from Lesson 5 – Expansion Formulae of Class 8 Maths (English Medium), Maharashtra Board.

All answers are explained in a simple and easy-to-understand method so that students can complete their homework, revise the chapter, and prepare confidently for exams.

Let's start solving Practice Set 5.1.

Solution,👇

1. (a+2)(a-1)

Formula: (x + a)(x + b) = x² + (a + b)x + ab

Here,

x = a

a = 2

b = -1

(a+2)(a-1) = a² + (2 - 1)a + (2 × -1)

                   = a² + a - 2

Answer: a² + a - 2

2. (m-4)(m+6)

Formula: (x + a)(x + b) = x² + (a + b)x + ab

Here,

x = m

a = -4

b = 6

(m-4)(m+6) = m² + (-4 + 6)m + (-4 × 6)

                     = m² + 2m - 24

Answer: m² + 2m - 24

3. (p+8)(p-3)

Formula: (x + a)(x + b) = x² + (a + b)x + ab

Here,

x = p

a = 8

b = -3

(p+8)(p-3) = p² + (8 - 3)p + (8 × -3)

                   = p² + 5p - 24

Answer: p² + 5p - 24

4. (13+x)(13-x)

Formula: (x + a)(x + b) = x² + (a + b)x + ab

Here

x = 13

a = x

b = -x

(13+x)(13-x) = 13²+(x-x)13+(x)(-x)

                       = 169+13x-13x-x²

                         =169-x²

Answer: 169-x²

5. (3x+4y)(3x+5y)

Formula: (x + a)(x + b) = x² + (a + b)x + ab

Take 

X = 3x

a = 4y

b = 5y

(3x+4y)(3x+5y) = (3x)² + (4y + 5y)(3x) + (4y × 5y)

                            = 9x² + 27xy + 20y²

Answer: 9x² + 27xy + 20y²

6. (9x-5t)(9x+3t)

Formula: (x + a)(x + b) = x² + (a + b)x + ab

Take X = 9x

a = -5t

b = 3t

(9x-5t)(9x+3t) = (9x)² + (-5t + 3t)(9x) + (-5t × 3t)

                          = 81x² - 18xt - 15t²

Answer: 81x² - 18xt - 15t²

7. (m + 2/3)(m - 7/3)

Formula: (x + a)(x + b) = x² + (a + b)x + ab

Here,

x = m

a = 2/3

b = -7/3

(m + 2/3)(m - 7/3) = m² + (2/3 - 7/3)m + (2/3 × -7/3)

                               = m² - 5/3 m - 14/9

Answer: m² - 5/3m - 14/9

8. (x + 1/x)(x - 1/x)

Formula: (x + a)(x + b) = x² + (a + b)x + ab

Here,

x = x

a = 1/x

b = -1/x

(x + 1/x)(x - 1/x) = x² + (1/x - 1/x)x + (1/x × -1/x)

                             = x² - 1/x²

Answer: x² - 1/x²

9. (1/y + 4)(1/y - 9)

Formula: (x + a)(x + b) = x² + (a + b)x + ab

Here,

x = 1/y

a = 4

b = -9

(1/y + 4)(1/y - 9) = (1/y)² + (4 - 9)(1/y) + (4 × -9)

                             = 1/y² - 5/y - 36

Answer: 1/y² - 5/y - 36

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