Page 318 - ICSE Math 8

Mental Maths Practice Time
1. (a) unlike (b) 7 (c) trinomial; two (d) 4; a 1. (a) 2x + 11x + 12 (b) 6x + 14x + 4 2
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2. (a) 4 (b) m (c) 5 y y
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(c) xy – 3y – 4x + 12 (d) 2x + 3x – 14x – 21
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Practice Time (e) x –49 (f) 12 –7x + x (g) 9x – 16y 2
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1. (a) 6p – 13pq + 1 2. –x y + 2x y – 2 2. (a) 16a + 24ab + 9b (b) 25x + 5x + 1
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3. (8x – 2y) units y 2 y 4y 2
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4. –6a + 5a – 7 5. 12l – 6lm + 2n 2 (c) 9x – 2xy + (d) 64x – 112xy + 49y 2
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6. 5x – 33x y – 46xy + 56x y + 12y 4 3. 7 4. 6 5. 7 6. (2y – 2) units
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7. (9p + 3p + 1) units Think Smart
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9. (a) –4x + 4y (b) –69x + 66y + 40 10. R + B – 5 1. 144 m 2. 2xy
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Think Smart
1. 10x(2x + 1); ` 5,690x(2x + 1) Chapter 14
2. (x –3) hours Exercise 14.1
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Chapter 13 1. (a) 3y (b) 4xy (c) 7x y (d) –2xy z (e) 9x y z u
2. (a) 2xy(3x + 1) (b) 2(x – 6)(x – 2)
Exercise 13.1 (c) 2x y(–2 + 4xy + xy ) (d) x(y + 3z + x)
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1. (a) y + 6y + 9 (b) 9x – 24xy + 16y (c) a + 2 4a + 4 (e) 16x y z (2xy – 3z ) (f) xy(ax + by + cz)
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(d) x y – 2x y + x y (e) 5.29x + 16.1xy + 12.25y 2 (g) 18x z (2y z – 3x + 5x y )
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x 2 xy y 2 169x 2 (h) 12x y(4y z – 3x) (i) (x + 4)(2x – 3)
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(f) − + 2. (a) 25x – 10xy + y (b)
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9 3 4 36y 2 (j) 3x(6x – 5y)(3 – 4x) (k) (x – 2y)(2x – 4y – 3)
(c) x – y (d) 4x + 4x y + y (l) (x – y)(l – 3m + n(x – y)) (m) x (3x –y)(x + 1)
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(e) 12.25x – 17.5x y + 6.25y (f) x − 4 (n) 2(x + y)(x – 4y)
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3. (a) 10,201 (b) 9,801 (c) 11,025 (d) 9,96,004 Exercise 14.2
(e) 2,52,004 (f) 10,04,004 (a) (a – c)(b + d) (b) (y + 2z)(6x – y)
4. (a) 1,300 (b) 3,575 (c) 1,560 (d) 9,999.84 (c) (b – a)(b + a ) (d) (a – x)(a – 2y)
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(e) 125 5. (a) 88 (b) 113 6. (a) 100 (b) 5 (e) (3y + x )(x – 2y) (f) (ya – x)(xa – y)
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1 1 1 (g) 4(p – q) (2p – 2q – 3) (h) (l + m )(x + y )
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(c) 100 (d) 7. x + 2 = 27; x + 4 = 727
4 x 2 x 4 (i) (1 – x)(1 – y) or (x – 1) (y – 1)
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8. x = 12 9. a + = ± 2 5; a – = ± 4
a a Exercise 14.3
10. 52 11. 38 12. ± 2 35 1. (a) 3(4x + 9y)(4x – 9y) (b) (13x – 8y)(20y – x)
13. (a) 16a – 81b (b) p – q (c) 25m – 49n 2 (c)  1 x + 1  1 x − 1  (d) 62l +  1  2l − 1  
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(d) y − 1   4 13  4 13     5m  5m 
y 4 (e) (a + 9b )(a + 3b)(a – 3b)
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15. (a) 42± (b) 2 5± (c) 658 16. 5 17. 9
(f) (16a + b )(4a + b )(2a + b)(2a – b)
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Exercise 13.2 (g) 8xy(x + y ) (h) 7(3xy + 1)(3xy – 1)
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1. (a) x + 8x + 12 (b) x – x – 12 (c) x – 12x + 35 2 1 3   1 3 
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9 3 (i) (2 + l – m)(2 – l + m) (j) b  a + c   a – c 
(d) 16x + 16x – 21 (e) 16 y + 2 2 y − 8 (k) (8p + 5q – 4)(8p – 5q – 4)  6 7   6 7 
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(f) x + 2 29 x + 1 2. (a) 240 (b) 76 (c) 12,000 (d) 400
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(g) 49x – 63x y + 18x y (h) l + 4 1 l − 2 3 Exercise 14.4
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2. (a) 10,815 (b) 11,448 (c) 9,312 (d) 9,690 (a) (x + 1)(x + 1) (b) (3x – 4y)(3x – 4y)
(e) 2,832 (f) 924 (g) 9,98,980 (h) 2,115 (c) (x + 2)(x – 6) (d) l +  1   l + 1 
Mental Maths   2     2  
1. 7 2. 5 3. 15 4. 29 (e) (3c + a – 2b)(3c – a + 2b) (f) –(2x – y)(3x – y)
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