In the column method of addition, like terms are placed one below the other and then added.
For example,
Add 15a + b + 3 + ab and 2ab – 5b + 3a – 6.
The given expressions are written such that the like terms are arranged one below the other as below:
15a + b + 3 + ab 3a – 5b – 6 + 2ab
Now, add the like terms as follows: 15a + b + 3 + ab
3a – 5b – 6 + 2ab
18a – 4b – 3 + 3ab
Arranging the terms in the descending order of exponents of the variables, the expression becomes 3ab + 18a – 4b – 3.
Thus, (15a + b + 3 + ab) + (2ab – 5b + 3a – 6) = 3ab + 18a – 4b – 3.