Question

HW Help: Using the following equation, find the center and radius:
x^2 - 4x + y^2 + 8y = -4
Select one:
a. The center is located at (-2, -4), and the radius is 4.
b. The center is located at (2, -4), and the radius is 4.
c. The center is located at (-2, -4), and the radius is 16.
d. The center is located at (2, -4), and the radius is 16.

Answer 1

b. The center is located at (2, -4), and the radius is 4.

Answer 2

You know why?

Answer 3

Why?

Answer 4

\[
x^2 - 4x + y^2 + 8y = -4 \\
(x^2 - 4x +4) -4 +( y^2 + 8y+16) -16 = -4 \\
(x-2)^2 + (y+4)^2=-4+16+4=16=4^2\\
(x-2)^2 + (y+4)^2==4^2\\
\]

Answer 5

That's it all worked out right?

Answer 6

Yes