Question

Using the following equation, find the center in radius of the circle. You must show all work and calculations to receive credit. X^2+2x+y^2+4y=20

Answer 1

x^2+2x+y^2+4y=20

(x^2 + 2x) + (y^2 + 4y) = 20

Using the completing the square method:

(x^2 + 2x + 1) + (y^2 + 4y + 4) = 20 + 1 + 4

(x + 1)^2 + (y + 2)^2 = 25

(x + 1)^2 + (y + 2)^2 = 5^2

This is in the format (x-h)^2 + (y-k)^2 = r^2, where (h,k) are the center of the circle and r is the radius.

Can you figure out what the center and radius are now?