Question 100047
question 2.
rewrite the formule in the form:
 x^2 - 20x + y^2 -16y = -64
next 
 x^2 -20x is the same as x^2 -20x +100 -100
 x^2 -20x +100 is the same as (x-10)^2
SO: x^2 -20x is the same as (x-10)^2 -100
In the same way:
 y^2 -16y is the same as (y-8)^2 -64
The complete formule becomes:
 (x-10)^2 + (y-8)^2 -164 = -64
or:
 (x-10)^2 + (y-8)^2 = 100
this is a circle with centre (10, 8) and radius 10