a/ Đặt a = x + 4

=> (a - 1)⁴ + (a + 1)⁴ = 16

=> a⁴ - 4a³ + 6a² - 4a + 1 + a⁴ + 4a³ + 6a² + 4a + 1 = 16

=> 2a⁴ + 12a² - 14 = 0

Đặt t = a² ( t\(\ge\) 0)

=> 2t² + 12t - 14 = 0

=> (t - 1)(t + 7) = 0

=> t - 1 = 0 => t = 1

hoặc t + 7 = 0 => t = -7 (loại)

Với t = 1 => a² = 1 => a = 1 hoặc a = -1

+) Khi a = 1 => x + 4 = 1 => x = -3

+) Khi a = -1 => x + 4 = -1 => x = -5

Vậy x = -3 , x = -5

1. Tìm lỗi sai và sửa lại:

1. Did you played tennis with Hanh yesterday?->play

2. Do you drawing a picture?->Are

3. He was in the flower fastival last weekend?->Was he

4. How often do you going swimming?->go

5. She want to goes shopping tomorrow.->want to go