Circles A and B have the following equations (x -4 )^2+(y -8 )^2= 25 and (x -2 )^2+(y -7 )^2= 49 . What is the greatest possible distance between a point on circle A and another point on circle B?

1 Answer
Aug 23, 2016

12+sqrt5

Explanation:

The general equation of a circle is (x-a)^2+(y-b)^2=r^2
Where the centre of the circle is(a,b) and the radius is r

The distance between the centres of the circles (4,8) and (2,7)
is sqrt5. The distance between the x coordinate is 2 , the distance between the y coordinates is 1 . From Pythagoras the distance is sqrt((2^2+1^2)
The radii of the circles are 5 and 7 hence the greatest possible distance.