-2px-qx+2py+qy+3ry-3rx

-2px-qx+2py+qy+3ry-3rx

=x(-2p-q-3r)+y(2p+q+3r)

=-x(2p+q+3r)+y(2p+q+3r)

=(y-x)(2p+q+3r)

2010-10-30 16:41:54 補充：
25(3x-2y)^2-9(2x+y)^2
=(15x-10y)-(6x+3y)^2
=(15x-10y+6x-3y)(15x-10y-6x+3y)
=(21x-13y)(9x-7y)

3x^4y-243y
=3y(x^4-81)
=3y(x^2+81)(x^2-81)
=3y(x^2+81)(x-9)(x+9)

-2a^4b^4+32c^4
=-2(a^4b^4+16c^4)
=-2[(a^2b^2+4c^2)(a^2b^2-4c^2)]
=-2(a^2b^2+4c^2)(a^2b^2-4c^2)

-2px-qx+2py+qy+3ry-3rx
=2p(y-x)+q(y-x)+3r(y-x)
=(2p+q+3r)(y-x)

25(3x-2y)^2-9(2x+y)^2
=25(9x^2-12xy+4y^2)-9(4x^2+4xy+y^2)
=225x^2-300xy+100y^2-36x^2-36xy-9y^2
=189x^2-336xy+91y^2
=(9x-13y)(3x-y)

3x^4y-243y
=3(x^4y-81y)

-2a^4b^4+32c^4
=2(-a^4b^4+16c^4)

25(3x-2y)^2-9(2x+y)^2


(15x-10y)-(6x+3y)^2

(15x-10y+6x-3y)(15x-10y-6x+3y)

(21x-13y)(9x-7y)

2010-10-30 15:59:21 補充：
3x^4y-243y

3y(x^4-81)

3y(x^2+81)(x^2-81)

3y(x^2+81)(x-9)(x+9)