中三數學題

3x^2 + xy - 2y^2
=(3x-2y)(x+y)

2007-10-06 14:15:50 補充：
其實用Cross Method就得3x　-2y　× x　＋y---------------3xy - 2xy = xy所以便是(3x - 2y)(x＋y)

3x^2 + xy - 2y^2
=x(3x)+xy-y(2y)
=(3x+2y)(x-y)