Phân tích các đa thức sau thành nhân tử :
1) x3- 7x + 6
2) x3 - 9x2 + 6x + 16
3) x3 - 6x2 - x + 30
4) 2x3 - x2 + 5x +3
5) 27x3 - 27x2 + 18x - 4
6) x2 + 2xy + y2 - x - y - 12
7) ( x + 2 )( x + 3 )( x + 4 )( x + 5 ) - 24
8) 4x4 - 32x2 + 1
9) 3( x4 + x2 + 1 ) - ( x2 + x + 1 )2
10) 64x4 + y4
11) a6 + a4 +a2b2 + b4 - b6
12) x3 + 3xy + y2 - 1
13) 4x4 + 4x3 + 5x2 + 2x + 1
14) x8 + x + 1
15) x8 + 3x4 + 4
16) 3x2 + 22xy + 11x + 37y + 7y2 + 10
17) x4 - 8x + 63
a)x3-7x+6
=x3+0x2-7x+6
=x3-x2+x2-x-6x+6
=(x3-x2)+(x2-x)-(6x-6)
=x2(x-1)+x(x-1)-6(x-1)
=(x-1)(x2+x-6)
=(x-1)(x2-2x+3x-6)
=(x-1)[x(x-2)+3(x-2)]
=(x-1)(x+3)(x-2)
2) x3-9x2+6x+16
=x3+x2-10x2-10x+16x+16
=(x3+x2)-(10x2+10x)+(16x+16)
=x2(x+1)-10x(x+1)+16(x+1)
=(x+1)(x2-10x+16)
=(x+1)(x2-2x-8x+16)
=(x+1)[(x(x-2)-8(x-2)]
=(x+1)(x-8)(x-2)
