Odpowiedź :
(x+5)(x-4) = x² - 4x + 5x - 20 = x² + x - 20
(3a+b)(2a-5) = 6a² - 15a + 2ab - 5b
3(a+2)(2a-1) = 3(2a² - a + 4a - 2) = 3(2a² + 3a - 2) = 6a² + 9a - 6
(x+5)(x-4) = x² - 4x + 5x - 20 = x² + x - 20
(3a+b)(2a-5) = 6a² - 15a + 2ab - 5b
3(a+2)(2a-1) = 3(2a² - a + 4a - 2) = 3(2a² + 3a - 2) = 6a² + 9a - 6