889. У простите выражение: a) (x - 2)(x + 2) - x(x + 5); 6)m(m - 4) + (3-m)(3+ m); B (4x-a) (4x + a) + 2x(x-a); )2a(a+b)(2a+b)(2a - b); д) (5а - 3c)(5a+3c) - (7c-a)(7c+a); e) (4b + 10c)(10c-4b) + (-5c + 2b)(5c + 2b); ж) (3x-4y)² - (3x-4y)(3x+4y); 3) (2a + 6b)(6b-2a) - (2a+6b)².

a) \[(x - 2)(x + 2) - x(x + 5) = x^2 - 4 - x^2 - 5x = -5x - 4\]

б) \[m(m - 4) + (3 - m)(3 + m) = m^2 - 4m + 9 - m^2 = -4m + 9\]

в) \[(4x - a)(4x + a) + 2x(x - a) = 16x^2 - a^2 + 2x^2 - 2ax = 18x^2 - 2ax - a^2\]

г) \[2a(a + b) - (2a + b)(2a - b) = 2a^2 + 2ab - (4a^2 - b^2) = 2a^2 + 2ab - 4a^2 + b^2 = -2a^2 + 2ab + b^2\]

д) \[(5a - 3c)(5a + 3c) - (7c - a)(7c + a) = 25a^2 - 9c^2 - (49c^2 - a^2) = 25a^2 - 9c^2 - 49c^2 + a^2 = 26a^2 - 58c^2\]

e) \[(4b + 10c)(10c - 4b) + (-5c + 2b)(5c + 2b) = 100c^2 - 16b^2 + (4b^2 - 25c^2) = 100c^2 - 16b^2 + 4b^2 - 25c^2 = -12b^2 + 75c^2\]

ж) \[(3x - 4y)^2 - (3x - 4y)(3x + 4y) = 9x^2 - 24xy + 16y^2 - (9x^2 - 16y^2) = 9x^2 - 24xy + 16y^2 - 9x^2 + 16y^2 = -24xy + 32y^2\]

з) \[(2a + 6b)(6b - 2a) - (2a + 6b)^2 = 36b^2 - 4a^2 - (4a^2 + 24ab + 36b^2) = 36b^2 - 4a^2 - 4a^2 - 24ab - 36b^2 = -8a^2 - 24ab\]