Geo4.6

From Example Problems
Jump to: navigation, search

If the radius of the circle x^{2}+y^{2}-8x+10y+k=0\, is 7,find the value of k.

In the given circle

g={\frac  {-8}{2}},f={\frac  {10}{2}},c=k\,

g=-4,f=5,c=k\,

The radius of the given circle is

{\sqrt  {(-4)^{2}+5^{2}-k}}=7\,

Squaring on both sides,

16+25-k=49\,

k=-8\,


Hence the value of k is -8.


Main Page:Geometry:Circles