1. ## Factorise

Factorise:

4 / x^2 - a^2 / b^2

2. Hello,

Note that 4 is 2²

Then if you have x and y as : x²/y², you can say that it is equal to (x/y)²

& finally, use the x²-y² factorisation

3. Originally Posted by stellina_91
Factorise:

4 / x^2 - a^2 / b^2
$= \left( \frac{2}{x} \right)^2 - \left( \frac{a}{b} \right)^2$.

Factorise using the difference of perfect squares formula.