Question

Write the equation for the circle that satisfies the following conditions: Center (-11,-10) and radius 8 units.
a. (x+11)^2 + (y+10)^2 = 64
b. (x-11)^2 + (y+10)^2 = 64
c. (x+11)^2 + (y-10)^2 = 64
d. (x+11)^2 + (y+10)^2 = 8
How do I find which answer is right?

Answer 1

You need to know the standard form for the equation of a circle so that you can identify the center and radius.

(x -( h)) ^2 + (y -( k))^2 = r^2

h = -11, k = -10, and r = 8

( x - (-11) ) ^2 + ( y - ( -10 ) ) ^2 = 8^2

(x + 11) ^2 + ( y + 10 ) ^2 = 64

a. (x+11)^2 + (y+10)^2 = 64 ---- Option A