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Question Number 5982 by Kasih last updated on 08/Jun/16
the center of circle in 2x+y−11=0  determine the equation of circle that  passing through (−1,3),(7,−1)
thecenterofcirclein2x+y11=0determinetheequationofcirclethatpassingthrough(1,3),(7,1)
Commented by Rasheed Soomro last updated on 08/Jun/16
the center of circle in 2x+y−11=0  determine the equation of circle that  passing through (−1,3),(7,−1)  −−−−−−−−−−−−−−−  2x+y−11=0⇒y=11−2x  Hence moving point of tbe line  (x,y)=(x,11−2x)  One of these  points is center of  the required circle and equidistant  from all tbe points of circle:  Hence,  Distance of(−1,3) from (x,11−2x)                          =Distance of(7,−1) from (x,11−2x)  (√((x+1)^2 +(11−2x−3)^2 ))=(√((x−7)^2 +(11−2x+1)^2 ))  (x+1)^2 +(−2x+8)^2 =(x−7)^2 +(−2x+12)^2   x^2 +2x+1+4x^2 −32x+64=x^2 −14x+49+4x^2 −48x+144  2x+1−32x+64=−14x+49−48x+144  −30x+65=−62x+193  32x=128⇒x=4  Therefore center of the required circle is  (x,11−2x)=(4,11−2×4)=(4,3)  Radius will be distance between (−1,3 ) and (4,3)  (√((4+1)^2 +(3−3)^2 ))=5    The equation of required circle      (x−4)^2 +(y−3)^2 =5^2 =25  Or another form       x^2 +y^2 −8x−6y=0
thecenterofcirclein2x+y11=0determinetheequationofcirclethatpassingthrough(1,3),(7,1)2x+y11=0y=112xHencemovingpointoftbeline(x,y)=(x,112x)Oneofthesepointsiscenteroftherequiredcircleandequidistantfromalltbepointsofcircle:Hence,Distanceof(1,3)from(x,112x)=Distanceof(7,1)from(x,112x)(x+1)2+(112x3)2=(x7)2+(112x+1)2(x+1)2+(2x+8)2=(x7)2+(2x+12)2x2+2x+1+4x232x+64=x214x+49+4x248x+1442x+132x+64=14x+4948x+14430x+65=62x+19332x=128x=4Thereforecenteroftherequiredcircleis(x,112x)=(4,112×4)=(4,3)Radiuswillbedistancebetween(1,3)and(4,3)(4+1)2+(33)2=5Theequationofrequiredcircle(x4)2+(y3)2=52=25Oranotherformx2+y28x6y=0

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