尽量快些,x,y是非0的实数,且X2+2xy-3y2=0,求—2Y/X=多少
问题描述:
尽量快些,x,y是非0的实数,且X2+2xy-3y2=0,求—2Y/X=多少
答
因为X²+2xy-3y²=(x+3y)(x-y)=0
所以x+3y=0,或x-y=0,
解得x=-3y,或x=y
当x=-3y时,-y/x=-y/(-3y)=1/3
当x=y时,-y/x=-y/y=-1