Selina Textbook Solutions: Algebraic Identities | Mathematics Class 8 ICSE PDF Download

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12. Algebraic Identities 
EXERCISE 12(A) 
Question 1. 
Use direct method to evaluate the following products : 
(i) (x + 8)(x + 3) 
(ii) (y + 5)(y – 3) 
(iii) (a – 8)(a + 2) 
(iv) (b – 3)(b – 5) 
(v) (3x – 2y)(2x + y) 
(vi) (5a + 16)(3a – 7) 
(vii) (8 – b) (3 + b) 
Solution: 
 
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12. Algebraic Identities 
EXERCISE 12(A) 
Question 1. 
Use direct method to evaluate the following products : 
(i) (x + 8)(x + 3) 
(ii) (y + 5)(y – 3) 
(iii) (a – 8)(a + 2) 
(iv) (b – 3)(b – 5) 
(v) (3x – 2y)(2x + y) 
(vi) (5a + 16)(3a – 7) 
(vii) (8 – b) (3 + b) 
Solution: 
 
 
Question 2. 
Use direct method to evaluate : 
 
Solution: 
Page 3


12. Algebraic Identities 
EXERCISE 12(A) 
Question 1. 
Use direct method to evaluate the following products : 
(i) (x + 8)(x + 3) 
(ii) (y + 5)(y – 3) 
(iii) (a – 8)(a + 2) 
(iv) (b – 3)(b – 5) 
(v) (3x – 2y)(2x + y) 
(vi) (5a + 16)(3a – 7) 
(vii) (8 – b) (3 + b) 
Solution: 
 
 
Question 2. 
Use direct method to evaluate : 
 
Solution: 
 
 
Question 3. 
Evaluate : 
 
Solution: 
Page 4


12. Algebraic Identities 
EXERCISE 12(A) 
Question 1. 
Use direct method to evaluate the following products : 
(i) (x + 8)(x + 3) 
(ii) (y + 5)(y – 3) 
(iii) (a – 8)(a + 2) 
(iv) (b – 3)(b – 5) 
(v) (3x – 2y)(2x + y) 
(vi) (5a + 16)(3a – 7) 
(vii) (8 – b) (3 + b) 
Solution: 
 
 
Question 2. 
Use direct method to evaluate : 
 
Solution: 
 
 
Question 3. 
Evaluate : 
 
Solution: 
 
 
Question 4. 
Use the product (a + b) (a – b) = a
2
 – b
2
 to evaluate: 
(i) 21 x 19 
(ii) 33 x 27 
(iii) 103 x 97 
(iv) 9.8 x 10.2 
(v) 7.7 x 8.3 
(vi) 4.6 x 5.4 
Solution: 
Page 5


12. Algebraic Identities 
EXERCISE 12(A) 
Question 1. 
Use direct method to evaluate the following products : 
(i) (x + 8)(x + 3) 
(ii) (y + 5)(y – 3) 
(iii) (a – 8)(a + 2) 
(iv) (b – 3)(b – 5) 
(v) (3x – 2y)(2x + y) 
(vi) (5a + 16)(3a – 7) 
(vii) (8 – b) (3 + b) 
Solution: 
 
 
Question 2. 
Use direct method to evaluate : 
 
Solution: 
 
 
Question 3. 
Evaluate : 
 
Solution: 
 
 
Question 4. 
Use the product (a + b) (a – b) = a
2
 – b
2
 to evaluate: 
(i) 21 x 19 
(ii) 33 x 27 
(iii) 103 x 97 
(iv) 9.8 x 10.2 
(v) 7.7 x 8.3 
(vi) 4.6 x 5.4 
Solution: 
 
Question 5. 
Evaluate : 
(i) (6 – xy) (6 + xy) 
 
Solution: