When we simplify algebraic expressions,** **we combine like terms.

Like terms are** **terms with matching letters.

**3a, 4a and a are like terms** because they are all multiples of a.

**2b, -b, -5b are like terms** because they are all multiples of a - even though some of them are negative.

2b and b^{2} are **not like** terms: 2b means 2 x b and b^{2} means b x b.

3b and 3 are **not like** terms: 3b is a multiple of b and 3 is not.

3b, 5c and -2 are **not like **terms: there is a multiple of b, a multiple of c and a number.

**Example**

Simplify **-4 + 3b + 4b - a + 2b + 6a + 3**

**Answer**

Look at the values before all the as (known as the coefficients): -a + 6a which are -1a + 6a

Combine them to get -1 + 6 = 5

So we get **5a**

Look at the coefficients of all the **b**s...... 3b + 4b + 2b which are 3b + 4b + 2b

Combine them to get 3 + 4 + 2 = 9

So we get **9b**

Combine the numbers which are** **-4 + 3 =** -1**

The answer is **5a + 9b - 1**

Let's have a go at some questions.