已知(x-y)/(x+y)=-1/2,则分式(x²+4xy+3y²)/(x²+2xy-3y²)的值等于
问题描述：
已知(x-y)/(x+y)=-1/2,则分式(x²+4xy+3y²)/(x²+2xy-3y²)的值等于
答
(X-Y)/(X+Y)=-1/2
(X+Y)/(X-Y)=-2
(X+Y)(X+3Y)/(X+3Y)(X-Y)
=(X+Y)/(X-Y)
=-2