Question

What is the center and radius of the circle with the equation x2 + y2 + 8x – 4y – 61 = 0?

Answer 1

Center: (–4, –2); Radius = 9
Center: (–4, 2); Radius = 9
Center: (4, –2); Radius = 9
Center: (4, 2); Radius = 9

Answer 2

I think its the 2nd choice.

Answer 3

Okie dokie. Thankyou(:

Answer 4

\[\large x^2 + y^2 + 8x – 4y – 61 = 0 \]
\[\large x^2 + 8x + y^2 – 4y – 61 = 0 \]
\[\large (x^2 + 8x + 16) + (y^2 – 4y + 4) – 61-16-4 = 0 \]
\[\large (x^2 + 8x + 16) + (y^2 – 4y + 4) – 81 = 0 \]
\[\large (x+4)^2 + (y-2)^2 – 81 = 0 \]
\[\large (x+4)^2 + (y-2)^2 = 81 \]
\[\large (x+4)^2 + (y-2)^2 = 9^2 \]

center is (-4,2) with radius 9