KEY CONCEPTS:

Difference of squares are binomials with the function of subtraction separating the 2 terms. NEVER a positive value.

When Factoring such special quadratics:
i.) square root the first term and the second term
ii.) place the first value as the first term of 2 sets of binomials and the second value as the second term
iii.) in one set of binomials write a negative, and the second set a positive.

ie. x^2-81 = (x+9)(x-9)