1) (x-6)(x+6) = x^2 + 6x - 6x - 36 = x^2 - 36
2) (7a^4 + 3b)(3b-7a^4) = 21a^4b - 49a^8 + 9b^2 - 21a^4b = -49a^8 + 9b^2
1) (x-6)(x+6) = x^2 + 6x - 6x - 36 = x^2 - 36
2) (7a^4 + 3b)(3b-7a^4) = 21a^4b - 49a^8 + 9b^2 - 21a^4b = -49a^8 + 9b^2