tolong no 19 sama 20 yah

19. Hasil 8(2x + y - 4) = 16x + 8y - 32 (c)

20. F(x-1) = 5-2(x-1) = 5 - 2x + 2 = 7 - 2x
      F(x) + F(x-1) = (5-2x) + (7-2x)
                           = 5 - 2x + 7 - 2x
                           = 12 - 4x atau -4x + 12 (d)