Đặt biến phụ dạng đa thức
1) x^4- 37x^2 + 9
2) (x^2 + x)^2 + 9x^2 + 9x+14
3) (x - y)^2 + 4x - 4y - 12
4) (x^2 + 3x)^2 +7x^2 + 21x + 10
5) (5x^2 - 2x)^2 + 2x - 5x^2 - 6
6) x^2 + 2xy + y^2 + 2x + 2y - 15
7) x^2 + 2xy + y^2 - x - y - 12
8) x^2 + 8xy + 16y^2 + 2x + 8y - 3
9) x^2 + 6xy + 9y^2 - 3(x + 3y) - 4
10) x^2 + 6xy + 9y^2  - 3x - 9y +2
11) x^2 - 4xy + 4y^2 - 2(x - 2y) - 35
12) 4x^2 + 4xy + y^2 + 10x +5m-6
13) (x^2 + x +1)(x^2 + x +2) - 12
14) (x^2 - x +3)(x^2 - x - 2) + 4
15) (2x^2 - x - 2)(2x^2 + x - 3) -12
16 (2x^2 - x- 1)(2x^2 - x +4) - 10
Đặt biến phụ dạng (x+a)(x+b)(x+c)(x+d) +e(với a+b=c+d)
​1) (x + 2)(x + 4)(x + 6)( x +8) + 16
2) (x + 2)(x+3)(x+4)(x+5) - 24
3) x (x +4)(x+6)(x + 10) +128
4) (x+1)(x +2)(x +3)(x +4)4) ( - 24 
5) x (x +1)(x+2)(x + 3) +1
6)( x- 1)(x - 3)(x - 5)(x - 7) - 20
7) ( x- 1)( x + 2)( x +3)( x + 6) - 28
8)x(x - 1)( x+1)(x+2) - 3
9) ( x+2)(x +3)(x-7)(x - 8) -144
10) (x-7)(x-5)(x-4)(x-2) -72
11)(x^2 +8x +12)(x^2 + 12x +32) +16
12) (x^2 + 6x +8)(x^2 + 8x +15) - 24
13) (x^2 +4x+3)(x^2 +6x +8)- 24
14) (x^2 - 6x +5)(x^2 - 10x +21)- 20
15)(x^2 +x -2)(x62 +9x - 18)- 28
16)(x^2 + 5x +6)(x^2- 15x +56)_144
17)(x^2 - 11x +28)(x^2 -7x +10)- 72