L':y=kx 交l1:4x+3y+1=0于A'( -1/(3k+4),-k/(3k+4) )交l2:4x+3y+6=0于B'(-6/(3k+4),-6k/(3k+4))A'B'=√2[5/(3k+4)]^2+[5k/(3k+4)]^2=22(3k+4)^2=25(1+k^2)18k^2+48k+32=25+25k^27k^2-48k-7=0(7k+1)(k-7)=0k=-1/7或k=...