Question

The equation of a given circle in general form is x^2+y^2-8x+12y+27=0. Write the equation in standard form, (x-h)^2+(y-k)^2=r^2, by completing the squares in the equation. Show your work in the table.

Answer 1

(x - 4)² + (y + 6)² = 5²

Explanation:

rearrange the general equation as follows

collect the terms in x and y together and place the constant on the right side

x² - 8x + y² + 12y = - 27

add (half the coefficient of the x/y term)² to both sides

x² + 2(- 4)x + y² + 2(6)y = - 27

(x - 4)² + 16 + (y + 6)² + 36 = - 27 + 16 + 36

(x - 4)² + (y + 6)² = 25

(x - 4)² + (y + 6)² = 5² ← in standard form