When you visit a market, you can see that, the vegetables and fruits of same kind are kept as separate heaps. Similarly, we can group the same kind of terms in an algebraic expression.

**Like
and unlike terms**

When you visit a market, you can see that, the vegetables
and fruits of same kind are kept as separate heaps. Similarly, we can group the
same kind of terms in an algebraic expression.

For example, the expression 7*x* + 5*x* + 12*x* – 16 has 4 terms but the first three terms have
the same variable factor *x*. We say that 7*x*, 5*x* and 12*x* are **like terms.**

However, the terms 12*x* and −16 have different variable factors. The term 12*x* has the variable *x* and the term −16 is a constant. Such terms are
called **unlike terms.**

Consider another example. In the expression 14*xy*−7*y*−12*yx*+5*y*−10, the terms −7*y* and 5*y* are like terms. Also, 14*xy* and −12*yx* are like terms. But, we cannot group the terms
14*xy*, 7*y* and − 10, as they do not have the same variables,
thus called unlike terms.

Hence, the terms of an expression having the same
variable(s) are called **like terms;** otherwise,
they are called **unlike terms.** The following
activity is helpful in identifying the like terms and unlike terms.

** **

**Try this**

Identify
the like terms among the following and group them: 7*xy*, 19*x*, 1, 5*y*, *x*, 3*yx*, 15, –13*y*, 6*x*, 12*xy*, −5, 16*y*, −9*x*, 15*xy*, 23, 45*y*, −8*y*, 23*x*, −*y*, 11.

*Like terms :*

*7xy, 3yx, 12xy, 15
xy *

*19x, x, 6x, –9x,
23x *

*5y, –13y, 16y, 45y,
–8y, –y *

*1, 15, –5, 23, 11*

** **

**Note**

Terms with the variables *xy* and *yx* are like terms, because of the commutative
property of multiplication *x* × *y* = *y* × *x*. Also, terms obey the commutative
property of addition, that is *x* + *y* = *y* + *x*.

Points to remember while identifying like terms
are as follows:

(i) In each of the term
ignore numerical co-efficient.

(ii) Observe the algebraic variables of the terms.
They must be the same. (Here the order in which the variables are multiplied should
not be considered).

Tags : Algebra | Term 1 Chapter 3 | 7th Maths , 7th Maths : Term 1 Unit 3 : Algebra

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7th Maths : Term 1 Unit 3 : Algebra : Like and unlike terms | Algebra | Term 1 Chapter 3 | 7th Maths

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