b) y/ 2x^2 -xy +4x/ y^2 - 2xy ;
Giải thích
b) y2x2−xy+4xy2−2xy
=yx(2x−y)+4xy(y−2x)=yx(2x−y)−4xy(2x−y)
=y2xy(2x−y)−4x2xy(2x−y)=y2−4x2xy(2x−y)
=(y+2x)(y−2x)xy(2x−y)=−(2x+y)(2x−y)xy(2x−y)=−2x+yxy;
b) y2x2−xy+4xy2−2xy
=yx(2x−y)+4xy(y−2x)=yx(2x−y)−4xy(2x−y)
=y2xy(2x−y)−4x2xy(2x−y)=y2−4x2xy(2x−y)
=(y+2x)(y−2x)xy(2x−y)=−(2x+y)(2x−y)xy(2x−y)=−2x+yxy;