Look at the expression \( 3xy-3y + 7x-7 \) . We observe that all terms of this expression do not have any common factor neither a monomial nor a binomial. But, we find that first two terms have monomial 3y as a common factor and the last two terms have a monomial 7 as common factor. Also, by taking 3y common from first two terms, we have

\( 3xy -3y = 3y(x—1) \)Taking 7 common from the last two terms, we have

We also notice that the binomial (x — 1) is common from these two groups of terms. Thus, by grouping the terms of \( 3xy – 3y + 7x -7, \) we have

\( 3xy-3y+7x-7 \) = \( (3xy-3y)+(7x-7) \)

= \( 3y (x -1) + 7 (x -1) \) = \( (3y+7)(x-1) \)

It follows from the above discussion that grouping of the terms of an algebraic expression may lead to its factorization. Also, grouping of terms is not unique. That is terms can be grouped in different ways. For example, the same algebraic expression can also be grouped as follows:

** **

**Example : \( n-7+7lm-lmn \)**