(x-6)(x+6) (3+x)(x-3) (3b-5)(3b+5) (5x+8y)(8y-5x) (m^5-n^3)(m^5+n^3) (5a^2b-1ab^2)(5a^2b+1ab^2) 4 4 (0.5x^3 + 0.2^4)(0.5x^3-0.2y^4)