Factories the following

x²– 81

In given expression

Both terms are perfect square

⇒ x² = x × x

⇒ 81 = 9 × 9

∴ x² – 81 Seems to be in identity a²-b² = (a + b)(a-b)

Where a = x and b = 9;

x² – 81 = (x-9)(x + 9)

Hence the factors of x² – 81 are (x-9) and (x-9)