1. **Stating the problem:** Factorise the given expression (though the expression is not provided, we will explain the general method). 2. **Formula and rules:** To factorise an algebraic expression means to write it as a product of simpler expressions. 3. **Common methods:** - Look for a common factor in all terms. - Use special products formulas like difference of squares: $$a^2 - b^2 = (a-b)(a+b)$$ - Factor quadratic expressions using methods like splitting the middle term or using the quadratic formula. 4. **Example:** Factorise $$x^2 - 9$$. 5. **Solution:** - Recognize this as a difference of squares: $$x^2 - 3^2$$. - Apply the formula: $$x^2 - 9 = (x - 3)(x + 3)$$. 6. **Explanation:** We rewrote the expression as a product of two binomials whose product equals the original expression. **Final answer:** $$(x - 3)(x + 3)$$