Class 8 - Mathematics
Algebraic Expressions and Identities - Exercise 9.5
Top Block 1
Question :1. Use a suitable identity to get each of the following products:
(i) (x + 3)(x + 3)
(ii) (2y + 5)(2y + 5)
(iii) (2a − 7)(2a − 7)
(iv) 
(v) (1.1m − 0.4)(1.1m + 0.4)
(vi) (a² + b²)(−a² + b²)
(vii) (6x − 7)(6x + 7)
(viii) (−a + c)(−a + c)
(ix)
(x) (7a − 9b)(7a − 9b)
Answer :
Question :2. Use the identity (x + a)(x + b) = x² + (a + b)x + ab to find the following products:
(i) (x + 3)(x + 7)
(ii) (4x + 5)(4x +1 )
(iii) (4x − 5)(4x − 1)
(iv) (4x + 5)(4x − 1)
(v) (2x + 5y)(2x + 3y)
(vi) (2a² + 9)(2a² + 5)
(vii) (syx – 4)(xyz – 2)
(i) (x + 3)(x + 7)
(ii) (4x + 5)(4x +1 )
(iii) (4x − 5)(4x − 1)
(iv) (4x + 5)(4x − 1)
(v) (2x + 5y)(2x + 3y)
(vi) (2a² + 9)(2a² + 5)
(vii) (syx – 4)(xyz – 2)
Answer :
Mddle block 1
Question :3. Find the following squares by using identities:
Answer :
Question :4. Simplify:
Answer :
Question :5. Show that:
Answer :
Question :6. Using identities, evaluate:
(i) 71²
(ii) 99²
(iii) 102²
(iv) 998²
(v) 5.2²
(vi) 297 x 303
(vii) 78 x 82
(viii) 8.9²
(ix) 1.05 x 9.5
(i) 71²
(ii) 99²
(iii) 102²
(iv) 998²
(v) 5.2²
(vi) 297 x 303
(vii) 78 x 82
(viii) 8.9²
(ix) 1.05 x 9.5
Answer :
Question :7. Using a² – b² = (a + b)(a – b) find :
Answer :
Question :8.Using (x + a)(x + b) = x² + (a + b)x + ab, find:
(i) 103 x 104
(ii) 5.1 x 5.2
(iii) 103 x 98
(iv) 9.7 x 9.8
(i) 103 x 104
(ii) 5.1 x 5.2
(iii) 103 x 98
(iv) 9.7 x 9.8
Answer :
