4X4 – 12X3 + 9X2 – ( 4X4 – 12X3 + 9X2 – 27X ) = 9 0,25Đ 4X4 – 12X3 + 9X2 – 4X4 + 12X3 – 9X2 + 27X = 9 0,25Đ 27X = 9 0,25Đ X = 1/3 0,25Đ
2. 4x
4
– 12x
3
+ 9x
2
– ( 4x
4
– 12x
3
+ 9x
2
– 27x ) = 9 0,25đ
4x
4
– 12x
3
+ 9x
2
– 4x
4
+ 12x
3
– 9x
2
4
3
2
4
3
2
4
3
2
4
3
2