Suppose that the functions f and g are defined for all real numbers x as follows

(f*g)(x) = (x-4)(2x+1) = 2x² + x - 8x - 4 = 2x² - 7x - 4

(f-g)(x) = x-4 - (2x+1) = (x-4)-2x-1 = -x - 5

(f+g)(3) = 3 - 4 + 2*3 + 1 = -1 + 6 + 1 = 6