已知直线l过点（2,4)且被平行直线L1x-y+1=0与直线x-y-2=0所截得的直线的中点在直线x+2y=0上,求直线L
<p>问题：已知直线l过点（2,4)且被平行直线L1x-y+1=0与直线x-y-2=0所截得的直线的中点在直线x+2y=0上,求直线L<p>答案：↓↓↓<p class="nav-title mt10" style="border-top:1px solid #ccc;padding-top: 10px;">陈桦的回答：<div class="content-b">网友采纳 解下方程组x-y+1=0x+2y=0得x-y+1=0与x+2y=0的交点A:x=-2/3,y=1/3同理,解下方程组x-y-2=0x+2y=0得x-y-2=0与x+2y=0的交点B:x=4/3,y=-2/3L被平行线x-y+1=0与x-y-2=0所截是线段的中点C,即AB的中点:x=(-2/3+4/3)/2=1/3,y=...
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