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解设:(1)圆C方程:(X-a)+(y-b)=r,a+(3-b)=r,(3-a)+(2-b)=r,a=b;a=1,b=1,r=5.所以:圆C的方程是:(X-1)+(Y-1)=5; (2)把Y=2X+m代入圆C方程得:(X-1)+(2X+m-1)=5,5x+(4m-6)x+(m-1)=0,∴x1+x2=-(4m-6)/5,x1x2=(m-1)/5,∴(x1+x2)=(4m-6)/25,∴(x1-x2)+4x1x2=(4m-6)/25,∴(x1-x2)=(4m-6)/25-[4(m-1)/5=(-4m-8m+16)/25,∴y1-y2=2(x1-x2),(y1-y2)=4(x1-x2),∵(x1-x2)+(y1-y2)=4,∴(-4m-8m+16)/25+4(-4m-8m+16)/25=4,∴-4m-8m+16=20,∴m+2m+1=0,m=-1.所以:m=-1.
1年前
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