This activity is about finding the Highest Common Factor (HCF) of two algebraic expressions.

**Example 1**

Find the HCF of 3p^{2}qr^{3} and 6pq^{3}r^{2}

__Answer__

Take each term in turn.

HCF of 3 and 6 is 3.

HCF of p^{2} and p is p.

HCF of q and q^{3} is q.

HCF of r^{3} and r^{2} is r^{2}.

So, the required HCF is **3pqr ^{2}**.

__Example 2__

Find the HCF of 4y(y - 7)(7y + 4) and (y - 7)^{2}(7y + 4)

**Answer**

The highest terms common to both are (y - 7) and (7y + 4).

So the HCF is **(y - 7)(7y + 4)**

Let's have a go at some questions.