A binomial expression is one that has two terms, such as 3a - 1

 

When we add and subtract binomials, we combine the letter terms and the numbers separately.

 

Be careful with negative signs and try to put the letter term first, for instance,  3a -1 rather than -1 + 3a.

 

Example 1

Simplify:

(3a - 1) + (2a + 7)

 

Answer

(3a - 1) + (2a + 7)

= 3a - 1 + 2a + 7

= 3a + 2a - 1 + 7

= 5a + 6

 

Example 2

Simplify:

(3a - 1) - (2a + 7)

 

Answer

(3a - 1) - (2a + 7)

= 3a - 1 - 2a - 7

= 3a - 2a - 1 - 7

= a - 8

 

Example 3

Simplify:

(3a - 1) - (2a - 7)

 

Answer

(3a - 1) - (2a - 7)

= 3a - 1 - 2a + 7 

 Did you spot that we had two negative signs which makes a positive?

= 3a - 2a - 1 + 7

= a + 6

 

Let's have a go at some questions now.