Evaluate:

$\Big(3x -\dfrac{1}{2y}\Big)$ $\Big(3x +\dfrac{1}{2y}\Big)$

$\Big(3x -\dfrac{1}{2y}\Big)$ $\Big(3x +\dfrac{1}{2y}\Big)$

Using the formula

[∵ (x + y)(x - y) = x² - y²]

$= (3x)^2 - \Big(\dfrac{1}{2y}\Big)^2\\[1em] = 9x^2 - \Big(\dfrac{1}{4y^2}\Big)$

Hence, $\Big(3x -\dfrac{1}{2y}\Big)$ $\Big(3x +\dfrac{1}{2y}\Big)$ = $9x^2 - \Big(\dfrac{1}{4y^2}\Big)$