F.3 Math

(x^2 + 2x)^2 -18(x^2+2x)+45
x^2(x+2)^2-18x(x+2)+45
(x^2+2x-3)(x^2+2x-15)
(x-1)(x+3)(x+5)(x-3)
________________________
x^2 - y^2 - z^2-2yz
x^2-(y^2+2yz+z^2)
x^2-(y+z)^2
(x-y-z)(x+y+z)
___________________
x^4-2x^2y^2+y^4
(x^2-y^2)^2
(x-y)^2(x+y)^2

Ifx + y =a, x-y=1/a

(1/a)^2*(a)^2
1/a^2*a^2
=1
__________________
x^2 - 4xy + 4y^2 -x + 2y
(x^2 - 4xy + 4y^2)-(x-2y)
(x-2y)^2-(x-2y)
(x-2y)(x-2y-1)

2010-11-11 21:46:17 補充：
.