a) (7x² - 4x + 8) - (4x² + x - 5) = 7x² - 4x + 8 - 4x² - x + 5 = (7x² - 4x²) + (-4x - x) + (8 + 5) = 3x² - 5x + 13
б) 5a(a⁴ - 6a² + 3) = 5a*a⁴ - 5a*6a² + 5a*3 = 5a⁵ - 30a³ + 15a
в) (x + 4)(3x - 2) = x*3x + x*(-2) + 4*3x + 4*(-2) = 3x² - 2x + 12x - 8 = 3x² + 10x - 8
г) (x + 5)(x² + x - 6) = x*x² + x*x + x*(-6) + 5*x² + 5*x + 5*(-6) = x³ + x² - 6x + 5x² + 5x - 30 = x³ + (x² + 5x²) + (-6x + 5x) - 30 = x³ + 6x² - x - 30
Ответ:
а) 3x² - 5x + 13
б) 5a⁵ - 30a³ + 15a
в) 3x² + 10x - 8
г) x³ + 6x² - x - 30