Multiply and simplify: (6x + 3y) (6x - 3y)

36x² - 9y²

Step-by-step explanation:

(6x + 3y) (6x - 3y)

(6x) ² - (3y) ²

36x² - 9y²

36x² - 9y²

Step-by-step explanation:

We see that the given expression (6x + 3y) (6x - 3y) looks just like the expression (a + b) (a - b). When multiplied out, this is a difference of squares identity that I highly recommend you memorise:

(a + b) (a - b) = a² - b²

Here, a = 6x and b = 3y, so plug these in:

(6x + 3y) (6x - 3y) = (6x) ² - (3y) ² = 36x² - 9y²