Question

(а+6)(а-3)+(а-4)(а+5)

Answer 1

$(a + 6)(a - 3) + (a - 4)(a + 5) = \\ = a {}^{2} - 3a + 6a - 18 + a { }^{2} + 5a - 4a - 20 = \\ = 2a {}^{2} - 4a - 38 = 2(a {}^{2} - 2a - 19)$