Geo4.3

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Find the equation of the circle which passes through (-7,1) and has centre (-4,-3).

The radius of the circle is

{\sqrt  {(-7+4)^{2}+(1+3)^{2}}}\,

{\sqrt  {9+16}}\,

The radius is \pm 5\,

Now the equation of the circle with centre (-4,-3) and radius 5 is

(x-(-4))^{2}+(y-(-3))^{2}=5^{2}\,

(x+4)^{2}+(y+3)^{2}=25\,

x^{2}+8x+16+y^{2}+6y+9=25\,

x^{2}+y^{2}+8x+6y=0\,

Main Page:Geometry:Circles