1) (3x-y)(3x+y)-(x-y)(x+y) = (3x)²-y²-(x²-y²) = 9x²-y²-x²+y² = 8x²
2) (11a+3b)(11a-3b)-(11a-3b)(3b-11a) = (11a-3b)(11a+3b-(3b-11a)) = (11a-3b)(11a+3b-3b+11a) =
= (11a-3b)*22a = 242a²-66ab
1) (3x-y)(3x+y)-(x-y)(x+y) = (3x)²-y²-(x²-y²) = 9x²-y²-x²+y² = 8x²
2) (11a+3b)(11a-3b)-(11a-3b)(3b-11a) = (11a-3b)(11a+3b-(3b-11a)) = (11a-3b)(11a+3b-3b+11a) =
= (11a-3b)*22a = 242a²-66ab