已知x-xy=20 xy-y=12,则x-y=( ),x+y-2xy=( ).

问题描述:

已知x-xy=20 xy-y=12,则x-y=( ),x+y-2xy=( ).

x - xy = 20 ①
xy - y = 12 ②
① + ② 得:
x - y = 32
① - ② 得:
x + y - 2xy = 8

已知x-xy=20 xy-y=12,则x-y=(32 ),x+y-2xy=(8 )
x-y=(x-xy)+(xy-y)
x+y-2xy=(x-xy)-(xy-y)