The equation x2+y2β4x+2y=b describes a circle. Complete the square to find the center of the circle. The center of the circle is ( , ) The radius of the circle is 7 units. What is the value of b in the equation? b=
Accepted Solution
A:
look to the coefficients on the middle terms (-4x and 2y)
divide each coefficient by 2 and square to determine what to add.
(-4/2)^2 = 4 needs to be added to complete the square for x.
(2/2)^2 = 1 needs to be added to complete the square for y.
add to both sides of the equal sign to keep the equation balanced.