A line and a circle intersect at $A$ and $B,$ as shown below. Find the distance between $A$ and $B$. The circle is x^2 + y^2 = 20. The line is y = -4.
x^2 + (-4)^2 = 20
x^2 + 16 =20
x^2 = 4
x= 2 or x = -2
A= (-2,4) B = (2,-4)
AB = [ 2 - -2 ] = 4
+420 
