合聚咖

合聚咖

很难的分解因式题

admin

原式=(2x-3y)^3 + (3x-2y)^3 - 125(x-y)^3

=(2x-3y+3x-2y)((2x-3y)^2-(2x-3y)(3x-2y)+(3x-2y)^2)-125(x-y)^3

=5(x-y)(7x^2+7y^2-11xy)-125(x-y)^3

=-5(x-y)(25x^2+25y^2-50xy-(7x^2+7y^2-11xy))

=-5(x-y)*3(2x-3y)(3x-2y)

=-15(x-y)(2x-3y)(3x-2y)