While adding or subtracting,

We add subtract like terms

 

Add 3 π‘₯ & 4π‘₯

 3π‘₯ + 4π‘₯

= π‘₯ (3 + 4)

= x × 7

= 7π‘₯ 

 

Add 8xy & 2π‘₯

8π‘₯y + 2π‘₯  

Since 8π‘₯y & 2π‘₯ are unlike terms

We cannot add them

 

Add 8π‘₯y, 4π‘₯y & 2π‘₯y

8π‘₯y + 4π‘₯y + 2xy

= xy (8 + 4 + 2)

= xy (14)

= 14π‘₯y     

 

Subtract 4n from 7n

7n − 4n

= n(7 − 4)

= n × 3

= 3n

 

Subtract 5ab from 11ab

11ab − 5ab

= ab (11 − 5)

= ab × 6

= 6ab

 

Now,

Suppose our expressions are bigger

 

Add 3x + 11 & 7x − 5

(3π‘₯ + 11) + (7π‘₯ – 5)

We group like terms together

= (3x + 7x) + (11 − 5)

 = 10π‘₯ + 6

 

Add (3x + 11 + 8z) & 7x − 5

(3π‘₯ + 11 + 8z) + (7x − 5)

= (3x + 7x) + (11 − 5 ) + 8z

= x (3 + 7) + (6) + 8z

= x(4) + 6 + 8z

 

= 4x + 6 + 8z

= 4x + 8z + 6   

 

  Subtract (a − b) from 3a − b + 4

(3a − b + 4) − (a − b)

= 3a − b + 4 − a + b

= (3a − a) + (−b + b) + 4

= (3a − a ) + (b − b) + 4

= 2a  + 0 + 4

= 2a + 4

  1. Chapter 9 Class 8 Algebraic Expressions and Identities
  2. Concept wise

About the Author

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Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.