SOLUTION: Find the center (h,k) and radius r of the circle. Graph the circle: x²+y²-4x-2y-20=0

Algebra ->  Graphs -> SOLUTION: Find the center (h,k) and radius r of the circle. Graph the circle: x²+y²-4x-2y-20=0       Log On


   

Question 969661: Find the center (h,k) and radius r of the circle. Graph the circle:
x²+y²-4x-2y-20=0
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!

x%5E2%2By%5E2-4x-2y-20=0
%28x%5E2-4x%29%2B%28y%5E2-2y%29=20...complete squares
%28x%5E2-4x%2Bb%5E2%29-b%5E2%2B%28y%5E2-2y%2Bb%5E2%29-b%5E2=20
%28x%5E2-4x%2B2%5E2%29-2%5E2%2B%28y%5E2-2y%2B1%5E2%29-1%5E2=20
%28x-2%29%5E2-4%2B%28y-1%29%5E2-1=20
%28x-2%29%5E2%2B%28y-1%29%5E2=20%2B4%2B1
%28x-2%29%5E2%2B%28y-1%29%5E2=25
so, h=2, k=1 and the center is at (2, 1)
r=5