An expression on the form a^2-b^2 can be factored to a product of two binomials. a^2-b^2=(a+b)(a-b) An example is the expression x^2-25 which can be written as x^2-5^2, and thus, be factored to a product of conjugate pair of binomials. x^2-5^2=(x+5)(x-5)