factor 25-81x^{2}

The given expression is a quadratic equation in the form of 25 - 81x^2.

To factor this quadratic expression, we first need to recognize that it is in the form of the difference of squares, which can be factored as (a^2 - b^2) = (a + b)(a - b).

Therefore, we rewrite 25 - 81x^2 as (5)^2 - (9x)^2.

Using the difference of squares formula, we can factor 25 - 81x^2 as:

(5 + 9x)(5 - 9x)

Therefore, the factored form of 25 - 81x^2 is (5 + 9x)(5 - 9x).