^2代表二次方
1.
(m+n)(p+q)-(m+n)(p-q)
=(m+n)[(p+q)-(p-q)]
= 2q(m+n)
2.
x(x+y)(x-y)-x(x-y)^2
=x( x^2 - y^2 ) - x ( x^2 - 2xy + y^2 )
=x [ ( x^2 - y^2 ) - ( x^2 - 2xy + y^2 ) ]
=x ( x^2 - y^2 - x^2 + 2xy -y^2 )
=2x (xy-y^2)
=2xy(x-y)
忘記抽出y了...囧
3.
-ab(a-b)^2+a(b-a)^2
=a[(b-a)^2-b(a-b)^2]
=a[(b^2-2ab+a^2)-b(a^2-2ab+b^2)]
=a(1-b)(a^2-2ab+b^2)
=a(1-b)(a-b)^2
好像怪怪的,不過算了
[ 瑋哥在2009-09-06 19:11重新編輯此帖 ]