### 7.4.3 Expanding and Factorising

This subsection is not completed yet, but in the meantime here are some practice questions.

Remember:
$a(b+c) = ab + ac$

Remember:
Expanding the difference of two squares: $(a-b)(a+b) = a^2 - b^2$

Remember:
Factorising the difference of two squares: $a^2 - b^2 = (a-b)(a+b)$

Remember:
Expanding a squared sum: $(a+b)^2 = a^2 + 2ab + b^2$ It’s a common error to forget the ‘cross-term’ $2ab$. It’s when we expand the square of a product that there’s no cross-term: $(ab)^2 = a^2b^2$.