'Bài 1'
$a)_{}$ $(6x+1)^2+(6x-1)^2-2.(1+6x)(6x-1)_{}$
$=36x^2+12x+1+36x^2-12x+1-2(6x+1)(6x-1)_{}$
$=36x^2+1+36x^2+1-2.(36x^2-1)_{}$
$=36x^2+1+36x^2+1-72x^2+2_{}$
$=4_{}$
$b)_{}$ $số_{}$ $max_{}$ $to_{}$
Bài 2
$a)_{}$ $x^2-x^3-4x+12_{}$
$=-x^3+x^2+2x-x+12_{}$
$=-x^3+2x^2-x^2+2x-6x+12_{}$
$=-x^2(x-2)-x(x-2)-6(x-2)_{}$
$=-(x-2)(x^2+x+6)_{}$
$b)_{}$ $x^4-5x^2+4_{}$
$=x^4-x^2-4x^2+4_{}$
$=x^2.(x^2-1)-4.(x^2-1)_{}$
$=(x^2-1)(x^2-4)_{}$
$=(x-1)(x+1)(x-2)(x+2)_{}$
$c)_{}$ $(x+y+z)^3-x^3-y^3-z^3_{}$
$=x^3+y^3+z^3+3x^2y+3xy^2+3x^2z+3xz^2+3y^2z+3yz^2+6xyz_{}$
$=3.(xyz+x^2y+zx^2z+xz^2+xy^2+y^z+xyz+yz^2)_{}$
$=3. [ xy.(x+z)+xz.(x+z)+y^2.(x+z)+yz.(x+z)]_{}$
$=3.(x+z)(xy+xz+y^2+yz)_{}$
$=3.(x+z). [ x.(y+z)+y.(y+z)]_{}$
$=3.(x+z)(y+z)(x+y)_{}$
$*_{}$ $nguyencuong18082006_{}$
$*_{}$ $Simple_{}$ $Love_{}$
