f.2 factorization

billyconan

plz&thx

[ 本帖最後由 billyconan 於 2009-6-28 02:39 PM 編輯 ]

98102257

兩條都要用到
a^3 - b^3 = (a - b)(a^2 + ab + b^2)
a^3 + b^3 = (a + b)(a^2 - ab + b^2)

6x^3 - 48y^3
=6(x^3 - 8y^3)
=6[x^3 - (2y)^3]  {a=x, b=2y}
=6(x - 2y)(x^2 + 2xy + 4y^2)

54y^3 + 2x^3z^6
=2(27y^3 + x^3z^6)
=2[(3y)^3 + (xz^2)^3]  {a=3y, b=xz^2}
=2(3y+xz^2)(9y^2 - 3xyz^2 + x^2z^4)