RD Sharma Solutions for Class 9 Maths Chapter 4 Algebraic Identities Exercise 4.4

RD Sharma Class 9 Solutions Chapter 4 Ex 4.4 Free Download

RD Sharma Class 9 Maths Chapter 4 exercise 4.4 available here. This exercise is about sum and difference of cubes. We have covered various examples to illustrate the use of these identities to simplify the products of algebraic expressions. RD Sharma Class 9 solutions cover important concepts that are more likely to be asked in examinations. Students can download RD Sharma Class 9 Maths Chapter 4 exercise 4.4 PDF from below link.

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RD Sharma Solution class 9 Maths Chapter 4 Algebraic Identities 18
RD Sharma Solution class 9 Maths Chapter 4 Algebraic Identities 19
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RD Sharma Solution class 9 Maths Chapter 4 Algebraic Identities 21
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RD Sharma Solution class 9 Maths Chapter 4 Algebraic Identities 24

 

Access Answers to Maths RD Sharma Class 9 Chapter 4 Algebraic Identities Exercise 4.4 Page number 4.23

Exercise 4.4 Page No: 4.23

Question 1: Find the following products:

(i) (3x + 2y)(9x2 – 6xy + 4y2)

(ii) (4x – 5y)(16x2 + 20xy + 25y2)

(iii) (7p4 + q)(49p8 – 7p4q + q2)

(iv) (x/2 + 2y)(x2/4 – xy + 4y2)

(v) (3/x – 5/y)(9/x2 + 25/y2 + 15/xy)

(vi) (3 + 5/x)(9 – 15/x + 25/x2)

(vii) (2/x + 3x)(4/x2 + 9x2 – 6)

(viii) (3/x – 2x2)(9/x2 + 4x4 – 6x)

(ix) (1 – x)(1 + x + x2)

(x) (1 + x)(1 – x + x2)

(xi) (x2 – 1)(x4 + x2 +1)

(xii) (x3 + 1)(x6 – x3 + 1)

Solution:

(i) (3x + 2y)(9x2 – 6xy + 4y2)

= (3x + 2y)[(3x)2 – (3x)(2y) + (2y)2)]

We know, a3 + b3 = (a + b)(a2 + b2 – ab)

= (3x)3 + (2y) 3

= 27x3 + 8y3

(ii) (4x – 5y)(16x2 + 20xy + 25y2)

= (4x – 5y)[(4x)2 + (4x)(5y) + (5y)2)]

We know, a3 – b3 = (a – b)(a2 + b2 + ab)

= (4x)3 – (5y) 3

= 64x3 – 125y3

(iii) (7p4 + q)(49p8 – 7p4q + q2)

= (7p4 + q)[(7p4)2 – (7p4)(q) + (q)2)]

We know, a3 + b3 = (a + b)(a2 + b2 – ab)

= (7p4)3 + (q) 3

= 343 p12 + q3

(iv) (x/2 + 2y)(x2/4 – xy + 4y2)

We know, a3 – b3 = (a – b)(a2 + b2 + ab)

(x/2 + 2y)(x2/4 – xy + 4y2)

RD sharma class 9 maths chapter 4 ex 4.4 question 2 Solution

(v) (3/x – 5/y)(9/x2 + 25/y2 + 15/xy)

RD sharma class 9 maths chapter 4 ex 4.4

[Using a3 – b3 = (a – b)(a2 + b2 + ab) ]

(vi) (3 + 5/x)(9 – 15/x + 25/x2)

RD sharma class 9 maths chapter 4 ex 4.4 solution

[Using: a3 + b3 = (a + b)(a2 + b2 – ab)]

(vii) (2/x + 3x)(4/x2 + 9x2 – 6)

RD sharma class 9 maths chapter 4 ex 4.4 question 1

[Using: a3 + b3 = (a + b)(a2 + b2 – ab)]

(viii) (3/x – 2x2)(9/x2 + 4x4 – 6x)

RD sharma class 9 maths chapter 4 ex 4.4 question 1 solution

[Using : a3 – b3 = (a – b)(a2 + b2 + ab)]

(ix) (1 – x)(1 + x + x2)

And we know, a3 – b3 = (a – b)(a2 + b2 + ab)

(1 – x)(1 + x + x2) can be written as

(1 – x)[(12 + (1)(x)+ x2)]

= (1)3 – (x)3

= 1 – x3

(x) (1 + x)(1 – x + x2)

And we know, a3 + b3 = (a + b)(a2 + b2 – ab)]

(1 + x)(1 – x + x2) can be written as,

(1 + x)[(12 – (1)(x) + x2)]

= (1)3 + (x) 3

= 1 + x3

(xi) (x2 – 1)(x4 + x2 +1) can be written as,

(x2 – 1)[(x2)2 – 12 + (x2)(1)]

= (x2)3 – 13

= x6 – 1

[using a3 – b3 = (a – b)(a2 + b2 + ab) ]

(xii) (x3 + 1)(x6 – x3 + 1) can be written as,

(x3 + 1)[(x3)2 – (x3)(1) + 12]

= (x3) 3 + 13

= x9 + 1

[using a3 + b3 = (a + b)(a2 + b2 – ab) ]

Question 2: If x = 3 and y = -1, find the values of each of the following using in identity:

(i) (9y2 – 4x2)(81y4 + 36x2y2 + 16x4)

(ii) (3/x – x/3)(x2 /9 + 9/x2 + 1)

(iii) (x/7 + y/3)(x2/49 + y2/9 – xy/21)

(iv) (x/4 – y/3)(x2/16 + xy/12 + y2/9)
(v) (5/x + 5x)(25/x2 – 25 + 25x2)

Solution:

(i) (9y2 – 4x2)(81y4 + 36x2y2 + 16x4)

= (9y2 – 4x2) [(9y2 ) 2 + 9y2 x 4x2 + (4x2) 2 ]

= (9y2 ) 3 – (4x2)3

= 729 y6 – 64 x6

Put x = 3 and y = -1

= 729 – 46656

= – 45927

(ii) Put x = 3 and y = -1

(3/x – x/3)(x2 /9 + 9/x2 + 1)

RD sharma class 9 maths chapter 4 ex 4.4 question 2 solution part 2

(iii) Put x = 3 and y = -1

(x/7 + y/3)(x2/49 + y2/9 – xy/21)

RD sharma class 9 maths chapter 4 ex 4.4 question 2 solution part 3

(iv) Put x = 3 and y = -1

(x/4 – y/3)(x2/16 + xy/12 + y2/9)

RD sharma class 9 maths chapter 4 ex 4.4 question 2 solution part 4

(v) Put x = 3 and y = -1

(5/x + 5x)(25/x2 – 25 + 25x2)

RD sharma class 9 maths chapter 4 ex 4.4 question 2 solution part 5

Question 3: If a + b = 10 and ab = 16, find the value of a2 – ab + b2 and a2 + ab + b2.

Solution:

a + b = 10, ab = 16

Squaring, a + b = 10, both sides

(a + b)2 = (10)2

a2 + b2 + 2ab = 100

a2 + b2 + 2 x 16 = 100

a2 + b2 + 32 = 100

a2 + b2 = 100 – 32 = 68

a2 + b2 = 68

Again, a2 – ab + b2 = a2 + b2 – ab = 68 – 16 = 52 and

a2 + ab + b2 = a2 + b2 + ab = 68 + 16 = 84

Question 4: If a + b = 8 and ab = 6, find the value of a3 + b3.

Solution:

a + b = 8, ab = 6

Cubing, a + b = 8, both sides, we get

(a + b)3 = (8)3

a3 + b3 + 3ab(a + b) = 512

a3 + b3 + 3 x 6 x 8 = 512

a3 + b3 + 144 = 512

a3 + b3 = 512 – 144 = 368

a3 + b3 = 368


Access other exercise solutions of Class 9 Maths Chapter 4 Algebraic Identities

Exercise 4.1 Solutions

Exercise 4.2 Solutions

Exercise 4.3 Solutions

Exercise 4.5 Solutions

Exercise VSAQs Solutions

RD Sharma Solutions for Class 9 Maths Chapter 4 Exercise 4.4

Class 9 Maths Chapter 4 Algebraic Identities exercise 4.4 is based on the sum and difference of cubes.

Important formulas:

  • a3 + b3 = (a + b)3 – 3ab(a + b)
  • or a3 + b3 = (a + b)(a2 – ab + b2)
  • a3 – b3 = (a – b)3 – 3ab(a – b)
  • or a3 – b3 = (a – b)(a2 + ab + b2)

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