Page 76 - Maths Skills - 8

74 Maths

Let’s Attempt

Example 1: Add : 4ab – 8a b, 12a b – 5ab and – 8a b + 18ab .
2
2
2
2
2
2
Solution: We have, (4ab – 8a b) + (12a b – 5ab ) + (– 8a b + 18ab )
2
2
2
2
2
2
= – 8a b + 12a b – 8a b + 4ab – 5ab + 18ab [Collecting like terms]
2
2
2
2
2
2
= (– 8 + 12 – 8)a b + (4 – 5 + 18)ab [Adding like terms]
2
2
= – 4a b + 17ab 2
2
Example 2: Subtract : 2 y 2 y 3 from 2 y 3 y y 5 .
2
3
3
2
7 5 3 7
 2 3   2 2 
Solution: We have,  y + y + y − 5 −  y − y + 3 
3
3
2
2

 3 7   7 5 
= 2 y 3 y y 2 y 2 y 3
3
3
2
2
5
3 7 7 5
53
= 2 y 2 y 3 y 2 y y [Collecting like terms]
2
3
3
2
3 7 7 5
2 2 3 2

= y 3 y 2 y ( 53)
3 7 7 5
= 14 6 y 3 15 14 y 2 y 8 = 8 y 29 y y 8
3
2

21 35 21 35
Exercise 5.1
1. Add.
(i) 12.5x – 15x + 7, 2.25x – 6x – 3, 5.6x – 2.5x + 13
2
2
2
(ii) 1 x 2 y 11z, 7 x 13z y, 23 x 4y
2
2
2
3 3 9 3
3
(iii) 19p 2 3q 2 5r , 2q 2 5p 2 17r , 1 p 2 q 2 r 2
2
2
7 5
(iv) 3x , − 7x , 1 x 2 (v) − 5ab , 3 ab , −1 ab , 1 ab
22
22
22
2
22
2
5 5 7 2
2. Subtract.
−1
(i) – 6y x from – 19y x (ii) xy z from 17xy z
2
2 2
2 2
2
5
1
(iii) p 2 p 1 from p 2 p2 (iv) –1 from 3x + 7y – 8z 2
2
2
2
3 3
(v) 3a + 7b – 6c + 4 from – 3a – 7b + 6c – 4