已知x+y=2分之1,xy=8分之3,求下列各式的值：(1)(x-y) (2)xy+xy
问题描述：
已知x+y=2分之1,xy=8分之3,求下列各式的值：(1)(x-y) (2)xy+xy
答
1) (x-y) =x-2xy+y =x+2xy+y-4xy =（x+y）-4xy =(1/2)-4×3/8 =1/4-3/2 =-5/4 (2)x^2y+xy^2 =xy(x+y) =3/8×1/2 =3/16