Evaluate:

$\Big(\dfrac{a}{2b} +\dfrac{2b}{a}\Big)$ $\Big(\dfrac{a}{2b} -\dfrac{2b}{a}\Big)$

$\Big(\dfrac{a}{2b} +\dfrac{2b}{a}\Big)$ $\Big(\dfrac{a}{2b} -\dfrac{2b}{a}\Big)$

Using the formula

[∵ (x + y)(x - y) = x² - y²]

= $\Big(\dfrac{a}{2b}\Big)^2 - \Big(\dfrac{2b}{a}\Big)^2$

= $\Big(\dfrac{a^2}{4b^2}\Big) - \Big(\dfrac{4b^2}{a^2}\Big)$

Hence, $\Big(\dfrac{a}{2b} +\dfrac{2b}{a}\Big)$ $\Big(\dfrac{a}{2b} -\dfrac{2b}{a}\Big)$ = $\Big(\dfrac{a^2}{4b^2}\Big) - \Big(\dfrac{4b^2}{a^2}\Big)$