a) 3x(x - 2) - 2x(x + 4) + 5x(x - 1) = 3x² - 6x - 2x² - 8x + 5x² - 5x = 6x² - 19x = x(6x - 19)
b) (x - 2)(x + 5) - (x + 1)(x + 3) = x²+ 5x - 2x - 10 - x² - 3x - x - 3 = - x - 13 =
- (x + 13)
c) (x + 4)(x - 3) + (x - 6)(x - 2) = x² - 3x + 4x - 12 + x² - 2x - 6x + 12 =
2x² - 7x = x(2x - 7)