Question 160196
Find an equation of the circle with center at(-8,7) and passing through (1,-4) in the form of {{{(x-A)^2+(y-B)^2=C}}} where A,B,C are constant. Then 
A=
B=
C= 
Ive already have the answers for A, B they are -8,7. I just 
want to know how to find C if the radius is not provided.
<pre><font size = 4 color = "indigo"><b>
So instead of:

{{{(x-A)^2+(y-B)^2=C}}}

write

{{{(x-(-8))^2+(y-(7))^2=C}}}

{{{(x+8)^2+(y-7)^2=C}}}

Think now: What haven't you used that was given?

Answer:  You haven't used this: "passing through (1,-4)"

So that means if you substitute (x,y) = (1,-4), the equation
must be true.  So let's substitute that:

{{{(x+8)^2+(y-7)^2=C}}}
{{{((1)+8)^2+((-4)-7)^2=C}}}
{{{(1+8)^2+(-4-7)^2=C}}}
{{{(9)^2+(-11)^2=C}}}
{{{81+121=C}}}
{{{202=C}}}

So write {{{202}}} for {{{C}}}

{{{(x+8)^2+(y-7)^2=202}}}

and you're done. The radius is {{{sqrt(202)}}}.

Edwin</pre></font></b>