Di jawab ya nomor 9 pakai cara

(i). (x-4)(3x+5)
=3x²+5x-12x-20
=3x²-7x-20 (benar)
(ii). (8m²-5n²)(8m²+5n²)
=64m^4-40mn^4+40mn^4-25n^4
=64m^4-25n^4 (benar)