4 x mũ 2 6 y y mũ 2 9 July 8, 2019 16 32 64 128 4 x mũ 2 6 y trừ y mũ 2 9 6xy - 4y + 6 - 9x 4 x 6 + 2 4^x + 6^x = 2*9^x 4 2x*(-6y)
