Page 140 - ICSE Math 6

Subtraction

Subtraction of like terms

The difference of two like terms is a term whose numerical coefficient is the difference of the numerical
coefficients of the given terms. For example,

(a) 4x – 2x = (4 – 2)x = 2x Maths Info
2
2
2
(b) 18a –10a = (18 – 10)a = 8a 2 Like terms along with their
13ab  13   35 13−  22 difference form a group of like
(c) 7ab – = 7 –  ab =   ab = ab terms.

5  5   5  5
Subtraction of unlike terms
Unlike terms cannot be subtracted to get a single term. So, we just write the unlike terms as the terms
of the algebraic expression with a subtraction sign. For example, if we subtract 2xy from 4a, we get
4a – 2xy.

Example 2: Subtract the following.
2
(a) 2pq from 22pq (b) 3ab from –13ab (c) 2rs from 2x
 –14 
2
(d) –4xy from  xy  (e) –12x from 20x 2
 3 
Solution: (a) 22pq – 2pq = (22 – 2)pq = 20pq
(b) (–13ab) – 3ab = (–13 – 3)ab = –16ab

2
(c) Since, 2rs and 2x are unlike terms.
2
\ Difference = 2x – 2rs
 –14   –14   –14 12+ 
(d)  xy  – (–4xy) =  xy + 4xy =   xy = –2xy

 3   3   3 
2
2
2
2
2
(e) 20x – (–12x ) = 20x + 12x = (20 + 12)x = 32x 2
EXERCISE 12.1
1. Add the following.
2
(a) 3x, 13x (b) a, 10a (c) 3pq, 2pq, –13pq
3
3 –2 − 2
2
2
(d) 8x , –10y 2 (e) x 2 , – y 2 , x 2 , 2y (f) 4pq, 6pq, pq
2 3 5
2. Subtract the following.
(a) 21q from 22q (b) 3x from –13x (c) –20a from –35a
1 –2
2
2 2 2
2
(d) 2xq from 3yz (e) 2 x y from 7 x y (f) 17a b c from 0
3. Simplify.
2
(a) 27m + (–35m) + 8m (b) –17xy + 3xy – 12xy (c) 2xyz + 3yzx – 5zxy
2
2
1 2
4. Subtract 23x yz + (–35x yz) from x yz.
2
2
2
5. Add 3xy + (–35xy) and 12x y – 7x y.
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