Question

What are the center and radius of the circle defined by the equation

x2 + y2 - 6x+8y +21 = 0 ?
-
O A. Center (3,-4); radius 2
O B. Center (-3, 4); radius 2
O C. Center (3, -4); radius 4
O
D. Center (-3, 4); radius 4

Answer 1

Radus: 2, Center (3,-4)

Explanation:

You first move the constant to the right then reorder the terms: x^2+y^2-6x+8y=-21.

You then complete the square: x^-6x+9+y^2=-21+9

Then factor: (x-3)^2+y^2+8y=-12

Then complete the square for the other term:

(x-3)^2+y^2+8y+12=-12+16

Then factor: (x-3)^2+(y+4)^2=4

4 is the radius squared, so the radius must be 2.

The center is the opposite of the constant in the parenthesis so the center must be (3,-4)

Answer 2

A


Step by step explanation This is how I got the answer to your question and I gave you the solution I hope this helps you out